In our office we run with a few different computers, and me personally, I have two computers - one for dev and email, the other for graphics and things like that. I installed IE 7 on my graphics machine, since I knew there was no turning back, and I also have Mozilla 2.0 and Opera 1.9 (I think these are the version numbers off the top of my head)
Some of the nuisance factors with IE 7 include the behaviour of popup windows - for those which are allowed it puts into a new tab, rather than a popup and it's very annoying sometimes, but I guess I can learn to live with it.
What I have found in reference to skinning, it's behaviour is closer to Mozilla than before, and what I'm finding now it's a bit of a nuisance at time flicking between two computers and three monitors, and three browsers, fiddling with css, but I do like how it works.
The other nuisance factor is the way the icons/labels work - I can't set to my own preferences, but overall, I like the browser, the tabbed viewing is great, and I'm pleased that it's more W3C compliant than before.
The disadvantage is that you do have now a version of IE that's different to the IE6 in how it renders,and once committed, can't change back to IE 6 to view the small changes that occur. I've spoken with a few people who have moved to IE7 but never have they suggested there are problems, but by that I mean - sure there might be some niggly things, but not enough for them to say they wish they hadn't moved forward.
I know this isn't much help but in the big scheme of things, I really like the new IE7, have found it to be stable (on my system anyway) closer to W3C compliant and it has some cool features that I think are long overdue.
Just my thoughts on the matter
Nina Meiers