I can do stand up wheelies on my old 1978 348 Montesa Cota trials bike no problem at all - well, I can't at the moment 'cos it's in the shed with no wheels on it
I've also done quite a bit of off roading on motocrossers and again, no problem with the front wheel being in the air.
On a big road bike I don't like 'em much. Don't mind the front coming up over hump back bridges or over the mountain, but even over the mountain I stand on the pegs and get my considerable weight over the front end (Motocross style) to stop it coming up too far.
One of the things that I do have from off-road bikes is a good sense of how far the front is coming up, and I did my first proper wheelie on my ST (with the bike at about 45 degrees) purely by accident. I was following Marko and Fordie through Uppingham, just the three of us coming back from Cadwell, and we got to the crossroads in the middle of town. Marko was leading and I was at the back as we trundled up to the traffic lights in first gear. As Marko crossed the lights they went amber, Fordie went across, but I wasn't sure whether the lights were going to change so I shut the throttle off quick and went for the brake, but then thought sod it, I'll go through as well and whacked the throttle open again just as the lights changed.
I'd created the perfect wheelie conditions by rolling along steady, snapping the throttle shut then whacking it open again. Sure enough, up came the front, nice and steady and I did my first proper big bike wheelie at the same time as crashing the red light. The good folk of Uppingham were not impressed and I'd just like to say that it's people like me that give bikers a bad name
In general though, even though I've repeated the process a couple of times (except for the red light bit) and can now do wheelies ranging from the pathetic to the moderate I prefer to keep the front wheel where it can steer me and stop me.
[Edited on 13-3-2006 by Jools]