I've been a big fan of HTC for a while; their Sense UI is really slick. I changed my previous Desire HD for a Sensation, which is essentially the same phone but dual-core.
There's not much to say, other than that its a slick device, good build quality, but a little boring with plain old factory software. I used revolutionary.io in order to S-off the device, and installed LeeDroid on it. The combination is very fast, powerful and a pleasure to use. Highly recommended!