I'll throw my hat in the ring...
As a big phone nerd I went out and got an HTC HD7 on launch day. Prior to that I've used every generation of iPhone, several Android phones, a couple Blackberries, and one unfortunate Windows Mobile phone.
WP7 is the biggest departure from conventional phones since the original iPhone. While the iPhone changed the way you interacted with the phone physically, WP7 changes the way you interact with the phone at a lower level. It's a new way to think about presenting information to the user.
So far my experience with the OS has been fantastic. Some people have told me I'm crazy, but I like the WP7 keyboard more than the iPhone's virtual keyboard. At the very least they are equal. Comparing the OS's themselves directly is very difficult because they don't play to the same principles. I know a lot of people are turned off by the way WP7 looks, but it really works with the philosophy that Microsoft it trying to stick to.
The point of WP7 is to get the most important information to the user first, everything else is secondary. The bold titles, mostly text interfaces, and live tiles on the start screen all play to that end. The email app is an excellent example of this. The largest text are the lists across the top (Unread, Urgent, All, etc.), the next largest text is the next largest important piece of information: the sender. It's a little disorienting at first, but you come to realize that your brain already functions like this.
One thing I am consistently amazed by is how quickly I get around the OS. The "Metro" style lends itself to finding what is most important the fastest, and could become a really beloved feature by many users, given the chance.
There are some ways, in addition to my opinion about the keyboard, that WP7 bests the iPhone. Notifications on WP7 are fantastic; not as good as Android's shade, but definitely better than Apple's disruptive pop-up system. The messaging apps are almost identical except for one key feature that pushes it to WP7 to me: time tagged messages. It's always irritated me that Apple doesn't time-tag their messages, and while it seems like a small thing, as a heavy texter I greatly appreciate it.
Of course, the Apple App Store blows Microsoft's Marketplace out of the water... For now. WP7 is on the right track, but until users and developers really bite into it, the iphone will stay App king. Another annoying feature of the marketplace that need fixed NOW is that you can't just search apps. If you search within the marketplace you are searching apps, music, and video, which is completely idiotic. A joint app is fine, but you've got to realize that users are there for different purposes and provide the access accordingly.
My experience with IE has been great. People are correct in that, when seeing small text zoomed out it renders it really weird. The thing that makes this a non-issue is that you wouldn't be able to read it at that level even if it were rendered perfectly. You're going to have to zoom in anyways, and when you do IE renders just fine. As for speed, in my tests it typically renders faster than android and the same as, and sometimes faster than, safari (to the same sites over the same wifi network).
The hardware is where the letdown happens. I've played with every available WP7 phone (in the US) with the exception of the Dell Venue Pro (which I am going to see tomorrow) and they just need help. I understand the OEM's hesitation to throw their best and brightest behind a new and unproven OS, but the devices are somewhat pathetic.
I've been living with the HD7, and while it's a good phone, I definitely have my complaints. The screen is acceptable at best, with a terrible viewing angle and dull color reproduction. It looks fine until you hold it up to another phone, at which point you will probably cry out of pity. The battery door cover snaps on instead of sliding into place, leaving a gap where you can see the SIM card through, and a bit of wiggle room (and no, it's not just MY device). The buttons suck because they are so shallow and are somewhat awkwardly placed on a slanted surface. The camera is OK (really, there isn't anything more to say).It is a good phone overall, but with a better screen, better fit, and better camera and buttons it could be great.
I've played with the Focus and Surround the most on AT&T. The LG isn't even worth mentioning. The Focus is just as hokey as all the other Samsung phones in the US. While it is probably the most complete package, I personally can't get past how crappy it feels. The camera is fantastic, however. The closest to the iPhone 4 I've seen on another phone. Everyone like to rave about the screen, and while it has an excellent viewing angle and brilliant colors, you can also count every. single. pixel... Sure, you have bright colors, but you've also got dots on everything... To each their own though, as my husband loves that screen.
The surround is extremely well made, with the same OK camera as the HD7 (maybe even a tad crappier). The screen is nice, and the sound output of the sound bar is, again, OK. But it's thick and heavy...
Ok, I'll stop now that I've written a novella.
For those tl;dr:
WP7 is an excellent start, the hardware needs help immediately. Hopefully Big Red will get some decent hardware in early 2011.