I can't disagree with AG about iOS, but I do work the CPU queue, and I have nothing but positive things to say.
The CPU queue isn't bad at all. It's not mind numbing at all. I get something different everyday. While most calls are things I can handle easily, that is a good thing, as it keeps my stats up and helps me be a standout on my team and in my queue. If you get CPU, you do need to have some technical knowledge, or your stats will be crap.
As far as opportunities, there seem to be quite a few. A few people from my team are cross training in iOS to be full time mentors on a rotation. I've had people rotate to account security, and I'll be training to be a team manager backfill. I've seen plenty of emails to try a rotation of some kind. I haven't seen too much movement to Tier 2, but at the beginning of my tenure, I saw about 25 people get hired to T2 for iOS. So the possibilities do exist.
I'd be happy to answer any questions that I can about the CPU queue.