I don't think you'll find the Intel graphics chip in the MacBooks limiting you when it comes to photo editing and other 2d tasks, at least not if you have enough system memory (since it's shared between graphics and applications), but the chip isn't really up to complex realtime 3d graphics.

I wanted to try out Second Life, for instance, but the Intel card in my MacBook doesn't cut it.

On the other hand, it's perfectly OK for less demanding 3d. Google Earth runs OK, for instance.