The 3.7 inch touch screen is phenomenal, it has 7 home screens so you never run out of home screen space to load up your apps (An issue I had a few times with my G1) There is also a very good widget which brings all your friends status updates from Twitter, Facebook etc.. right to your home screen. The contacts sync up with your facebook profile, Outlook and G-Mail services. This caused a slight error for me the first time when I uploaded the contacts from my old phone to G-Mail and ended up getting everyone on there twice. Also it pulls your contacts photos off social media and adds them as their contact picture which is a nice touch as i can never be bothered to take pictures of everybody.
The handset itself has a good feel, it is sleek and looks modern enough to give the iPhone a run for its money but has enough weight to make it feel good and robust, Battery life has so far proved good as I charged it when it first arrived and then it went 18 hours of very heavy usage whilst I was setting everything up and I am now showing 3/4 battery after 22 hours of "Average" Usage.
The Best feature - easily the 1 Ghz Processor, when i heard it had such a large processer I was sceptical if it would make a difference, it really does, from the second you log in you notice how much faster this phone is than any other smart phone you may have used. Now obviously no phone is completely perfect so I really want to find a fault to report on, So far the only negative for me is that it does not have a full keypad, I have always had a connection to my keypads and have never liked the virtual keyboards, however even this is slightly mitigated as it has a predictive text recognition software which is very good meaning i can actually use the on screen board as fast as I can type on my G1's full keypad.
I am sure that before long I will find something that annoys me, so I will be sure to be a lot more balanced once I have found it. But for now the only thing I can think is that there is so much I am not using it, there is a chance I have finally found a mobile device where in fact it is me that doesn't have enough features.
I have the full specs here from the HTC website