I have a 2007 FD3 and when I bought it 3 years back it's battery had been replaced by the previous owner with cells from Insight. It is running fine up to now and after talking to some guys at Stafford it seems that NiMH battery cells are common for IMA equipped models. So battery cells from Insight, GP1, Fit Shuttle etc.seems to be compatible with the Civic.
Like alpha17 mentioned the car is a bargain for the price with the options and comfort.
Agree with alpha17, if you are not planning to use it for long commutes my advise would be to stay away from the FD3 and go for a FD1, FD4 or the Lancer EX as without long commutes there's pretty much no use in owning any hybrid! (no fuel savings but battery replacement cost after the battery deteriorates)