Just downloaded the latest version released earlier this week. The release notes state (I'm just highlighting the speed improvements):
-OpenMP speedup of Star Mask image reading code.
-Huge speedup of final image display by using much larger rectangles and OpenMP speedup of the bitmap extraction code.
-Speed up star registration by updating progress indicator once every 25 iterations instead of each iteration.
-Computing Final Picture using Kappa-Sigma Clip processing is now about 50 times faster!
-Computing Final Picture using Auto Adaptive Weighted Average is now about 43 times faster!
-Entropy Weighted Average complete stack of 50 lights is now about 20 times faster on my laptop, down from 4hrs 22min to 12min 55 sec.
-Three times performance improvement in star registration.
-Miscellaneous other performance tweaks.
Trying it out now on some images I want to restack with drizzle and it is COOKIN' .