Hi!
some first comparison pictures can be found here:
http://www.astrotreff.de/topic.asp?TOPIC_ID=73354
It's a german forum, but I guess one can see the difference anyway. Differences are not THAT big. For me, the software just feels better and I get better details over the whole picture while Registax tends to sharpen details in one area and blur others, regardless of how many alignment points I specify. Also, alignment times with Registax with 40 or 50 alignment points are really high, while one can wait for Avistack to align with 500 points.
About downloading the IDL VM, I don't know. Did you activate your account and log in? If everything fails, we may PM and get things done
