I am not sure if this answers your question.
The float is actually the same as what is meant on your shimano and look pedals. The difference is where Shimano and Look has fixed float of either fixed (0 degree), 4.5 degree or 9 degree determined by the cleat used where the float on the speedplays are adjustable via setting screws on the cleat itself.
Speedplay pedals have no engagement mechanism on the pedal itself and all of it is instead being placed on the cleats itself.

From the pic above, you can see 2 adjustment screws that does 2 things
1) Centering of your foot
2) Adjustment of float play
The float adjustment is reached by adjusting the top and bottom screw in and out. If screw in both screws until it has no gaps, then there will be no play. If you screw out both screws, there will be a small gap in between them and you will have some amount of play. That is why it is micro adjustment while other pedal systems rely on the fixed system of their cleats.
Not trying to sell speedplay here but, here is where the strong points of speedplay comes into play (no pun intended). Where whatever adjustments (fore/aft, lateral, centering) you want to make to shimano and look cleats. You have to loosen all 3 screws and by making either adjustment, you mess up the other 2 settings as the cleat actively moves around. On the speedplay cleats, you adjust fore/aft, lateral and centering all in 3 independently. Some views this as a pain but it all makes up for accurate adjustments that does not affect one another when changes are made.
Adjustment of the cleats starts with fore/aft positioning of the base plate

On top of the base plate lies the cleat assembly itself which has only allows lateral (left/right) movements.

By doing this, the combination of cleat + base plate adjusts the cleat perpendicular to the shoe. Adjustments to the foot centering is then later made via the adjustment screws to set the centering of your foot. The only problem i can see is that if you were to play around with your settings especially fore/aft...then it might become a slight pain as you have to take off the cleats to reach the base plate.
The pedal is also lower in stack height because the main assembly is on the shoe rather than the pedal itself. And the pedal recesses into the cleat assembly on the shoe making the shoe to pedal spindle interface stack lower compared to other pedal systems. Some argues this improves power transfer but i think it's bull.
In some ways it is a fussy pedal, where if you notice they utilize phillips screw heads for their mounting screws as opposed to allen key holes. This is a problem because as you walk with the shoe, the phillips screw head wears out and further down the road, it becomes close to impossible to make adjustments to the cleats as the screws are no longer usable. So, any settings you need to do you will have to set it early on and make peace with whatever you have done earlier (or you can get the cleat cover for walking around). They have a reason for this phillips type screw as they claim that the phillips screw heads will not allow users to tighen the cleats down that much as over tightening the screws prevents the cleats from working properly. The screws also has tabs built into their thread so you know when to stop tightening when you feel a faint click.
Also it is not cheap to maintain where the cleat itself costs SGD75 per pair and every 5000 miles also you have to inject grease into the spindle via the grease port in order to maintain grease on the needle bearings used in the pedals which does not last as long as conventional ball bearings. Parts failure like spindle or the bow tie is replaceable, but not cheap and not sure if the shop might have it. There is also some misconceptions about power transfer on the small pedal body, but that i believe you can google to find out more as it is an interesting debate.
The offset is they do allow for many adjustments like a extended base plate kit for moving the cleats further back for a more mid-foot setting. Wedges (feet that is not parallel to the ground), stacks (different leg length), different spindle length among other things that makes speedplay a very adjustable pedal system.
The other thing i see lacking comparing it to shimano and look is that it lacks the tension adjustment feature which is none existent on speedplay. The only claim is that the stainless steel version has an alternate track version meant for track use which they claim has stiffer entry and release which i don't see how it works since the mechanism is on the cleats and the cleats look exactly the same as the replacement ones i bought.
I use the zero stainless steel pedal due to rider weight limitation of 185 pounds on any models above that, i won't choose any models further up anyways due to the price. You might be able to use the others like top of the range Nanogram if you prefer to. But it will cost way into the 4 figure amount (MYR) just to save weight. The cromo version is not made in US as far as i understand and only stainless steel versions and above are US made.
If plainly just to save weight, i don't think speedplay is the correct pedal to go for. It is definitely made for people who wants refined adjustments.
p/s: some reading
http://www.speedplay.com/index.cfm?cgid=3&...ction=cg.thumbsinstallation of the cleat
http://www.speedplay.com/index.cfm?fuseact...g.thumbs&cgid=1some brainwashing BS
http://www.speedplay.com/index.cfm?fuseaction=home.chooseHaha thanks for the informative reply. You are cycling wiki and you better be the Speedplay distributor in Malaysia quickly! Anyway I took the bait. If I understand correctly the cleat positioning is totally customisable independently of the fore/aft, lateral and centering. The 15 degree of float range seems a lot though and I like it loose as long as it is not going to jump of accidentally on a sudden hard pedalling.
Well I'm not going for the Nanogram whatever that's freaking expensive. However the titanium one looks to fit in the budget range but since I have forego the weightweenine route (never start the ww journey), I'd go with the normal zero and save me some costs. It's nowhere to be found in any lbs here so I have to resort to online shopping.
so will your next bike be Giant?

NO. But I know my die hard Giant friend would love to
Anyway, correct me if I'm wrong. This whole stiffness thingy for a bike is only matters when your body weight comes into play. Let say I weigh at 64kg, vin ann weigh at 100kg. We both riding the same bike, we push the same 1000w of power sprinting uphill, the bike will flex less for me rather than when it comes under the heavy force by a much heavier vin ann.
Meaning to say, a much heavier rider will need more stiffer frame to achieve the same level of bike performance (frame flexing) with a lighter rider who ride a less stiffer bike.
In conclusion, I would be happy to get an SL4 even if months ahead in the TDF that SL5 is spotted in the peloton with a much improve stiffness and shits because I know SL4 is good enough already.