I have fond memories of this machine. it was my first computer...
Well, actually, the TMS 9900 processor had a 15 bit address bus and a 16 bit data bus -- You were required to read/write 2 bytes at a time to memory. The machine wasn't really that slow, even if it was a bit short on RAM... The BASIC interpreter, however, was painfully slow (and that includes "Extended Basic"). As mentioned above, it had a great graphics processor which supported hardware sprites. It's sound chip was the same as the one in the IBM PCjr, which supported up to 3 tones/noise at the same time, of varying volume and duration.
IMO, the best game available for it (rememeber, old home computers were console game systems too) was Parsec.