Hang on for a little while if you want an iPhone 4, Apple are bringing out a cheaper iPhone 4. Basically the same phone but without the expensive, fragile and easy to scratch front and back panels. It will have plastic instead, so will be tougher, lighter and cheaper, but still the same iPhone 4.
However, if you have brain of your own, go to a shop and try some phones out.
Love my HTC Wildfire, works great, does everything I need, cheaper and smaller than an iPhone. But its all down to personal taste.