I have owned and have been using a Palm Pre since December 2009, so I am well placed to make a comment. Like many, I was undecided between an iPhone and the Pre. On paper, the Pre is a fantastic phone. Many of the features are better than the iPhone. Unfortunately, in practice the Pre doesn't live up to it's ability. The operating system slows down very quickly. The service reception is just awful in comparison. On a minibus recently trying to get google maps up, I couldn't, the iPhone users on the bus were all using google maps with no problems. I'm on O2 so I don't know how it performs on other networks but trying to hold a conversation for any length of time is impossible. The worst feature by far though is the battery. I have to put the phone on charge every single day. If I don't do it before 8pm in the evening, it will often shut down. I make less than 60 mins of calls per day and as I work most days, do not use the browser or other battery draining features for long periods either.
It is a great phone with loads of great features, but a bit more testing by Palm would have probably been beneficial. A great effort though.
The Palm Pre Plus is being launched which has a faster processor and improved battery, so that will probably make this the great phone it should be.