Most of the y400/y500 users are having the same weak wifi issue.
It is because of the wireless adapter lenovo is using in these laptops.
Unless you change the wireless adapter, there is no other way to improve it.

using 15.3.1 driver.. okie so far... fixed the problem

the above driver is for intel.. i guess u need to wait until atheros update their driver

out of curiosity, u model from which country? intel n2230... i tot all model uses this...

^I remember looking through the full tear down guide of Y580, the layout of the wifi attenna is not typical (some sort of new layout scheme).
Till this day, I still strongly suspect this new layout may have lead to wifi signal interference (hence the weak wifi is not solely due to adapter) in Y580 (and may have pass the curse to Y500 )

But I don't bother to test my theory since my Y580 is also plug into LAN at home

Its seem that the local set with atheros wifi adapter facing the same issue like China set according to chinese forum http://ideapad.it168.com/thread-2903884-1-1.html

You can try out the solution suggested by them. do let us know whether it work. 

You unlock the wireless adapter white list in bios?

Follow the pics if cant get it. 
Here the simple guide according to them: 
Try option 2 first:


Alternatively, you can try to change your modem setting to 802.11g only instead of 802.11bgn mixed. This will limit ur wifi strength.


do let us know the status.

Local Y400 come with W8 and default wifi driver 10.0.0.209, you reinstall to Win7 and unofficial wifi driver 10.0.0.75?
May be its a drivers issues. 
If use Win7, try Lenovo official wifi drivers 9.2.0.439 below for Y480's atheros wifi since no official Win7 drivers for Y400.
It seem Y480 user dont have any problem with Atheros wifi adapter using default drivers.
http://download.lenovo.com/consumer/mobiles/0pwm03ww.exe

Great review, I agree 100%.  I am also having the keyboard issue.  My keyboard will enter in some random characters and I can almost always replicate the issue by hitting the "6" key on the numpad.  I hit it enough times, and it will throw a "`6" or "``".  This is completely random so I'm thinking that either the keyboard is defective or there's some interference happening.  The same sort of issue I had with the Elan touchpad which I have since fixed.  Let me know if you come up with a solution for the keyboard and I'll do the same!

If i send to authorized service partners is it okay ? :/ quite scared they bomb me with the bill.
Same wifi issues and also wanna upgrade HDD

On the spot service? :/ or send in for few days?

download from the link provided by Mr_47. i also downloaded from thr.