I am considering getting an iPhone. Not until May, when my current contract expires, so I have some time to think about it. Should I wait for something even more spectacular?
So far, July seems to be when Apple unleashes a new/updated iPhone, but unless something crazy happens, all iPhones will run the 3.0 software. The 3G model has additional hardware capabilities over the original one, including GPS (there are numerous apps that take advantage of the positioning capability) and the next iPhone will do too (should be at least the faster processor from the iPod Touch). There's lots of rumours, and some reasonable evidence, that Apple is again going to update the iPhone in July as the "droppings" of an "iPhone 2,1" have been seen around San Fran*. No one knows exactly when or how though, but it would be worth your while, IMHO, to wait until July to see what, if anything, comes out.
This is what drives people nuts about Apple, in that they do not have a product "arc". They have a product "flat line", so that you pay the same price on the first day of sale as you do on the day before the model is rendered obsolete. The only fall back you have is a 30 day return policy.
Keep an eye on macrumors.com. I find they do a good job of keeping you informed as to the latest gossip, while not getting themselves overly steamed up about it. Can't say the same for those who frequent their forums - yours truly included.
* The original iPhone was "1,1" and the 3G was "1,2". An iPhone "2,1" suggests there might be something quite big happening.