Haven't used it as the primary (only) yeast in a beer, but I used champagne yeast in my last Russian Imperial Stout that finished in the mid 12% - low 13% ABV range. I tossed in one pack well after any visible signs of fermentation had disappeared in case it would ferment out anything my primary yeast didn't (didn't want bottle bombs), then used a 2nd pack at bottling. For the record the gravity didn't change by even a single point with the first addition (don't have my records right here beside me but I believe the FG was around 1.028). So in my one experience I would say that the frequently repeated line of "it'll dry your beer out" isn't accurate at all. It actually was slow to carb the beer as well but it did work...or something did, as there's no way to know for sure it wasn't just simply leftover primary yeast...something like 6 months after the initial pitching.
One thing I'll say for champagne yeast if you want to experiment with using it to push the gravity in a beer...it's cheap. I'd suggest starting with a yeast that gives the character you want, then using the champagne yeast in the latter part of fermentation, for incremental feeding, or for bottling.