I have been very happy with my set of Velo Orange Crazy Bars. Technically, my set have been discontinued and replaced (rather unfortunately I think). The new version of the Crazy Bars have shorter horns and less sweep; this may be preferable to some, but not me.
My bars have 45° of sweep and several inches of forward extension. The sweeps are useful for an upright position, both comfortable and with good control; from this position, unweighting the front wheel is rather easy, even with a packed down bike. On the other end, the horns are long enough to change my position to a flat-back aero pose; though I can't reach the brakes, I can chug along into the wind for hours (switching back to the grips to reach for a brake or shifter is easy enough, but it does break the rhythm). I can also ride with palms rested on the flat bar at the base of the horns (even with my usual clutter); this position is the most natural, is close to the controls and helps keep the shoulders out of the wind, but doesn't allow for a strong grip -- it's 'resting' on the bars.
That said, these bars are most useful for long days in the saddle, or mixed terrain rides. If you're not needing an aero tuck, or you don't need to sit bolt upright for a bit, they are a bit overkill. Though I can ride rough terrain, these bars don't provide nearly as much leverage as a flat bar; in the really chunky stuff, it feels like it takes too much pressure from the thumb to keep the bars straight. If your ride is mostly tech, I'd opt for much less sweep; nonetheless, there are a lot of places mountain bikes can go where I'd take an alt-bar!
