From cheap Chinese batteries should if possible stay away because I have personally collected so very bad experience. If it is 3000 mAh on these things, perhaps more than in 2100 actually present ... And then the short life: - (((
The extent of the long-term test and the life of SONY's looks, can be at this point, of course, do not tell. A prerequisite for a long battery life are like getting a discharge of the battery and a complete full-charging. Although NiMH (nickel metal hydride cell) not a typical 'memory effect' such as in the obsolete NiCd batteries (nickel cadmium cells) occurs, this does not harm 'trimming' the batteries and extend the lifespan considerably mE. A slight self-discharge during prolonged time spent in these batteries can also not be avoided.
Unfortunately, a detailed instruction manual is missing in such battery packs - but it would certainly not a bad property - especially for first time users or older semester ...
---- Addendum dated 15.03.2012 ----
The batteries are for many charge cycles still fully functional!
I can therefore still also recommend a follow-up