I have yet to regret doing so thus far. I'm having so much of a better time on there than I ever did on Alliance. The players have been friendlier in my experience and while leveling I actually have been getting ganked a lot less (though this might be because I learned to level in different zones). While leveling, players have also been very quick to help me when I actually was getting ganked. Ever since coming back after taking a break in June, I've taken it upon myself to revenge gank Alliance players who try to give levelers a hard time during my travels leveling up the Mining skill. My only gripe is that I've lost BGs more on Horde than I have on Alliance, but it's a small gripe considering I prefer PVE much more.
I dunno if Horde really is truly the PVE faction, but I've only had one failed RDF group since rerolling Horde. ONE. I mained Horde on retail, and I'm glad I am doing so on Icecrown now. Unfortunately, I have yet to get into a raid and the closest I have gotten thus far to one here are Alliance City Raids and ICC rep farms (which I have yet to complete). Even so, I'm still having a pretty good time. Ever since coming back from my break two weeks ago, I got the For The Horde Achievement after doing flawless city raids.
PS: For those about to ask why I rolled Alliance in the first place, I wanted a change of pace because I rolled Horde A LOT in retail.
Lok'tar Ogar!