My Experience
After much looking around and consideration I acquired a Probox 5200 mAh. It runs fine. They claim to use Sanyo cells which has a reputation. After being in use for a few months I think that they are good. Prices are relatively higher but sadly they are not being restock.
Just bought another, the bigger 7800mAh. Hope it is as good as the first. Been on shop shelves a while and unlike Romoss they dont come pre-charged so have to do full charge of 8 hours. Keeping fingers crossed but from my experience of my first purchase I think it will proved to be OK.
I do notice there is another brand that also quite good. Enerpad.

Them more decent brands that I am aware of:-
1. Probox - use Sanyo cells, premium look, so so build
2. Eneloop - Own Sanyo branded powerbank, supplied with charger
3. Enerpad
4. Romoss - Utilise Samsung, SDI for the premium model, great build
5. Gigabyte also uses Japan cells, not sure what brand tho

This post has been edited by shea2812: Jan 31 2014, 08:57 AM

I do hope some of forummers can post long term reviews of various models of powerbanks that we see many people use to give us a rough guide as to which are good buy and which are trash....
A decent powerbank can extend some of our mobile devices so that they can yields more months of services and delays purchase for upgrades while waiting for the right stuff to be released.

Good to see more info being presented ere. Just purchased another Romoss siling 2 5200mAh for a fren. The casing build is chosen because that particular fren is quite rough in handling his stuffs. The small form factor is bonus. And got a single cell Valore 2200mAh powerbank as freebie from Challenger. Neat for my old torchlite Nokia that i still use regular for voice calls... ha ha. Valore is a singapore brand that uses Samsung cells think. Challenger carries them.
Reason why I have a need for powerbank is that I am now using N7 to take on mobile duty instead of lugging a 13" laptop and I use the N7 with a BT keyboard, With a powerbank there is a guaranteed one day runtime with a smartwatch also paired to it. Neat.