as mentioned… it depends what you use the phone for.
If your primary use is email, then BlackBerry is a real contender; however it is awful for almost everything eles, especially anything that require web connectivity. And if you do go for the berry, avoid their touch screen version. it’s not very responsive and the operating system, so far, isn’t very good.
For a good all round Smart Phone that does most things well, you really have two main choices Apple and Android. And whilst I’m a huge Apple fan, here I’d go with an android device over Apple.
The Apple is a great piece of kit with great software, however, as it doesn’t license it’s software to other manufacturers, it will alway be a niche player in the market. As a result the options on a multi-hardware platform (that collectively will have multiple times more users than apple) will be significantly greater.
Of the Android devices, the Samsung is the best option. HTC is great, but build quality of the Samsung is better. And if you can afford to wait, Samsung are launching a new phone soon (I think it’s called Vibrant) – out in the US in June a bit later here.
I’d avoid anything Windows based at the moment. There’s too much up in the air with them (tie in with nokia, potential to buy out nokia, just bought skype etc.) to suggest a real solid plan of action. They need to settle themselves down and see wht they produce in about 18months time.