I was wondering if anyone has worked out what kind of polygon budgets are sensible for the different phones and devices -- from the hardware specs the 3GS looks quite capable, but I'm less confident about the 3G. It does depend on shading complexity and things as well, but it's usual to start out with something in mind, at least for your planning

How many poly's do you usually run per frame? And what kind of target framerates do you use?

The numbers are so different it's hard to say. But I always keep a FPS counter and sometimes switch to glPolygonMode(GL_POINTS, GL_FRONT_AND_BACK). This highlights each point and helps you see where most points are. I try to keep game's frame rates to more than 50 FPS during development.