Like you I share the perspective of a low hours glider pilot. I found it valuable to do upset and aerobatic training last winter and I plan to do more in the future.

http://www.azsoaring.com/training/

If you're the typical power pilot with add-on glider rating, you are probably not yet comfortable with steep turns, spin recovery, recovery from inverted flight, but familiarity with these maneuvers will give you a better chance of keeping a cool head when the unexpected happens in the air. For example, when you have an opportunity to fly in mountain wave you will want to be comfortable flying through rotor. Steep turns are useful in 50% of thermals.

The best occasion for learning aerobatics seems to be in mountain wave (because the wave allows you to recover lost altitude, rinse and repeat), but you really don't need lift because a neophyte can take a high tow and have a "full day" of aerobatic flying in 20-30 minutes. The intensity compensates for the short duration.