[quote name='dejeckt']wouldn't buying a separate ps2 more convenient? less hassle of worrying if this ps2 game will run on my ps3 or not?[/quote]
PS2 games are upscaled and look slightly better on a PS3, plus you don't need to mess around with memory cards for your game saves. Also, you hookup 1 single unit to the HDTV instead of 2 separate units taking up additional inputs.
Having said that, not all PS2 games will run flawlessly on PS3, unless you happen to have the 20/60GB model.