It will fit in your pocket just fine. It's really not that big.
First impressions are rather shocking. I'm an apple guy. So I have the Mac, iPad, and iPod. So doing something as simple as putting a picture from the phone on the Mac takes an extra step or two. What I've found is there are several ways to do the same thing. I haven't messed with the music yet. I will say where apple simply works, this makes you do the work. If that makes sense? It's something I know I will get used to.
The phone itself seems pretty good. The camera is down right awesome. That was the deciding factor for me between this and the HTC one. I think I made the right choice. It's pretty fast as well. The menus took some getting used to but I like the complete control I have over the phone. So that's the nice part and the advantage of making the switch.
I do think I like the email system of the iPhone better. The only thing I really don't like about the phone is the back of the device. The large white plastic back looks and feels cheap. I thought the black color looked even more cheap. Although I'm sure it's cheap to replace should you need to.
I just need to get comfortable with it. I ordered a 32 gig micro SD card to throw in it. I also had an old iPod laying around so I'm using that for my SUV's sync system. Which I wanted to do anyways because I kept forgetting to grab my phone. I will report back in a couple days with an update. I wouldn't say there is a huge issue though going from iPhone to this.