There's no real limit to the number of entries in your address book. The address book capacity is only limited by the 64 MB of memory.
Every professional review (including CNET's) of the 8800 can be found here:
I have found great info on CNET about the 8800 but nothing regarding the address book capacity. I now use a PDA to store 3500 contacts. How many will I be able to keep on the 8800 and still function?