First few impressions:
The pebble blue is beautiful. Even though people are complaining about the plasticky look, the glossy back in this color looks great, and the slightly two-tone curve along the side is awesome. I did not use a case for my old Epic and it did get a few scuffs (though it did survive a couple bad falls), but putting a case on this is making me sad.
I hate the physical button in the context of such a big phone. I played with the Evo LTE at the store to get a sense of what it is like to operate a phone of a similar size with one hand, and reaching with my thumb to hit the capacitative buttons was fine. However, actually having to push down a physical button is uncomfortable (I have small hands), and this is made worse by a case.
Still getting used to the Touchwiz/ICS hybrid. There are a crazy number of customization options, gesture controls, voice commands (both Google and S-Voice) that will take a long time to figure out what works best for me. Some of the setting menus are huge! Luckily, I am a geek and working through these is part of the fun of getting a new phone, though I can imagine this being intimidating to someone new to the OS.
Because I heard the battery life is good, I am doing all the things I was never able to do on my Epic and get a full ~15 hour day of use: live wallpaper, multiple widgets, push e-mail, auto-brightness. The performance is still great, only limited by the speed of my internet connection, but we'll see how the battery holds up over a whole day of use today.
As for those people saying "I will never pre-order" because of the delays, I only have the phone in my hand because I pre-ordered. I saw what happened with the original Evo, so wanted to make sure I was not in the position of having to wait beyond the early adopters. You exchange the inconvenience of them charging you at the time of the pre-order with the knowledge that you will be among the first to get a phone that we all knew would be in incredibly high demand. Who knows when they will actually get them in the store.