If u'd care about making good apps. Then i'd recommand buy a cheap 3GS for testing from craigslist. Or an ipod touch or something.
So u can at least test on a real device.
If u read through the books of learning objective C/iPhone they will explain u why.
Because the simulator uses the RAM of ur laptop. ntot he actual ram, so it's not good to test. only for quick tests 🙂
Well, good luck anyways 😉