Look and feel
I am so, so impressed by the way the HTC Sensation feels and looks in my hand. It is the perfect weight...just substantial enough but not too heavy to be burdensome. The back actually is composed of three different materials, one that feels cooler and metallic, one that feels rubbery, and a top section that is also slightly rubbery but not quite as rubbery as the bottom section. You can tell that HTC put a hell of a lot of effort into designing a sleek case for their phone and it fits the hardware like a glove. The screen is slightly raised around the edges, which means that when you put it on a hard surface, it is somewhat well protected against scratches. Oh, and about scratches: haven't had any problem with this at all. The screen looks as good as new, even after I've spent weeks with it in my pocket rubbing up against my keys and iPod Nano.
Speakers / Screen
It's been said many times before, and is likely true, that the HTC Sensation's screen isn't viewable from as many angles as the SGS2, but the screen seems bright enough to me, and viewing angles are impressive. I honestly haven't watched too many movies on the device but my games look stunning, as does my aquarium wallpaper. Sound quality is excellent.
Antennae / WiFi
I can tell my antennae is more responsive than the one on my previous phone. Even though the reception in my house isn't fantastic, whenever the reception is better, the bars go up almost instantaneosly, which is helpful because I am often jumping out on to the deck to make a phone call, and the phone responds almost immediately to the fact that there's better reception out there. That said, there is a death grip problem! I've tested it out, and whenever you hold the phone in a death grip, the number of available WiFi networks decreases. This is a real problem.
There are plenty who bemoan that Sense 3.0 is all superficial and isn't functional enough to be enjoyable on a daily basis. I think they're wrong. The Sense 3.0 software has continued to be interesting to me. I just wish HTC would create more widgets, because I'm already a bit sick of the one's I've installed. HTC IS OBSESSED WITH WEATHER. This is very true. But I haven't gotten sick of any of the weather animations, and am always happy when it's rainy or thundery because I know I'll get to see some cool animations. I don't use firmware like Friend Stream, and I think HTC Locations is a much uglier version of Maps, so I don't use that either. "Mirror" is a silly piece of firmware that allows you to take a look at yourself and get the piece of parsley out of your teeth. It's a cute little feature, and one that no one says too much about. The HTC Sensation also has an awesome flashlight, that is truly incredibly bright.
Once, the lockscreen didn't load and I had to drag the ring through a dark screen before it would start. I've also had some issues with the weather app doubling the animations on top of each other. Both of these problems resolved themselves without needing any technical support. There's also the death grip problem.
Well, that's about all I can say right now. Overall, I'm very happy with my purchase. I think that I have a few different perspectives just because I've had the phone for a while now. Hope you found them helpful