Whenever I've seen lasers used, I rarely if ever recall seeing them aimed into an area where people would be.
I see a lot of shooting UP, or back up into the backstage area to a screen, or onto a front screen. Or, in the case of a arena show I attended at Arco Arena in 1991, there is this flat area between levels where there are ads. They aimed lasers there and did this sine wave stuff. But never have I seen a show where lasers were pointed directly INTO the audience.
My concern is exactly the same as SerraAva pointed out: eye damage.
This is one of the reasons why I don't want to deal with lasers. First, my clients aren't requesting them, so there is no demand at the moment. Second, as SerraAva points out, you really need fog or haze to properly get the laser effect. Heck, there are some lights that suck on their own but you ad fog and these suckers come to life. Lasers are definately in that category. Third, in small venues, where I can aim it is a bit of an issue. Side walls, or ceilings, or back walls. If I do ceilings, a lot of places have mirrored ceilings or else it's too high up to be effective as an effect, especially without fog or haze. If I aim to a side wall, often those walls are way too far out, so I have to aim a bit too much up and again, it gets lost. If I aim to a back wall, it's often too short a throw for what I'd prefer. I never have screens or sheets to project onto, so that's never an option.
Lasers are cool. I wouldn't mind getting a mover or two with laser capability. But as I said, I don't get calls for it. I also rarely use fog. It's not a good combination for me at this point in time.
As far as fog vs. haze: Both have their applications, including both in the same event. Given a choice, I think I'm looking towards the Antares hazer for my choice, mainly because haze has less current draw than a fogger. Haze gives you that super thin fog that lets your lights always "show up" super cool. If you need an effet, that's where fog comes in because fog coming in on its own is a cool effect. Fog is more of an "as needed/on demand" thing, while haze is a constant on thing.
I can't say I totally agree with Jingles as far as haze being better than fog. It depends on the exact nature of how things are being used. Given a choice, I'd go with haze.
Fishy smelling haze? I find that old fluid picks up odors if not kept well sealed.