Having owned many phones in the past, I can honestly say that this is one of the best.
Firstly, be aware that it runs Windows Phone 7. This means that there are limitations such as having to use Zune to copy pictures, music etc between the phone and your PC. There is not the selection of apps on Android or the iPhone but there are still a lot of apps.
Windows Phone 7 is a great system especially if you are into communications - text and email - and social networking. It has a fantastic and fast web browser and is very smooth and slick. It has some great games and is brilliantly simple.
The Radar is a seriously solid device. It feels rock solid in the hand and nice to hold. The build quality is simply fantastic and better than pretty much anything else out there. It is extremely fast and responsive with a decent and very sensitive screen. I find the size to be perfect. I find the sound quality for calls and for music to be well above average. The battery life is also above average for me.
The software enhancements made by HTC to Windows Phone are worthy too.
The negatives for me are that the handset is a tad bland in its design and is a little thicker than I would like. The power button could be nicer to use, especially if it were metal like the camera button. There is only 8Gb of storage, about 6.5Gb of which is free and that has to store your apps, app data, music, podcasts, pictures and videos. It is simply not very much.
If you are looking for a mid range Windows Phone handset, this is the one to get. There is no compromise on performance and no compromise on quality.