While I can't answer Brad's question about touring acts, I wanted to share my experience with hazers and foggers.
First, I had an older Antari 1200 Z fog machine (no longer in production) that worked great right up until the heater clogged and the pump failed. But it was very old and was used a lot before I ever got it. (And I used the hell out of it!) So I really can't say anything bad about Antari.
That being said, I currently own 3 of the Chauvet Hurricane 1300 fog machines, and they are GREAT! Yeah, yeah, say what you will about Chauvet being consumer grade (and not professional grade). They still work really well and have never let me down. One thing I will suggest, however, is that if you go with a standard fog machine, use Froggy's Swamp Juice exclusively. This stuff is the best fog fluid I've found, bar none. And believe me I've tried a lot of different brands (over a dozen). Froggy's has the best hang time, and I've never had it clog a machine.
If you want a hazer (for venues that don't allow fog, for example), I do agree that some of the more expensive units mentioned above are great. But they have a price tag to match!
I currently own a pair of the American DJ Haze generators that Brad suggested above, and if you are on a budget you should seriously consider one. They run between $400 and $450 per unit on-line, and I really like them. The output is close to that of a DF-50, maybe slightly less, and the hang time is the same. Also, they are rated to run continuously, and I have run mine all day (and well into the night) at SELEM without any issues.
I was warned to test mine when I first got it though. Evidently they (American DJ) had a problem when some of these units would be dead right out of the box. As Brad said, if this happens just send it back for a replacement. But if it works when you first fire it up, it will run forever.
Adam