The iPad's older siblings, the iPhone and the iPod Touch, came from nowhere in 2009 to be the hottest gaming platforms in the industry. Games on the iPhone/iTouch are cheaper and often more fully featured than their Nintendo DS and PSP counterparts, without an excessive sacrifice when it comes to controls, despite the necessity to do everything with touchscreen gestures. The Apple store has over 20,000 games listed, compared to over 600 PSP titles and over 3,600 for the Nintendo DS.
Game developers are certainly excited about the prospect of developing for the iPad, since it's more powerful, and has higher resolution than, the iPhone and the iPod touch, with the same effective digital distribution channel and the same popular touchscreen controls.
From a usability standpoint, I see early development efforts for the iPad falling short, and I'm certainly not alone. No matter how much more powerful or pretty the iPad is, the fact is that it's a bit too large to work as a standard handheld, and porting titles straight from the iPhone, the DS or the PSP will cause massive control and usability issues. It's large enough to interfere with many game control schemes, and heavy enough that extended play sessions will be hard on the wrists if gamers are forced to play with it the same way they play with a smaller iPhone.
Games with simpler control schemes like Popcap's excellent line will translate well, but more complex games -- indeed, the very games the developers are looking forward to bringing to the mass audience that the Apple Store offers -- could well fall flat because of these usability issues, if developers don't invest in creative new control schemes that cater directly to the iPad itself.