Mueller is a less known name compared to the Bushnell Elite, Nikon Buckmaster, Zeist, Leupold, etc. I have 2 of them and I am quite pleased with how they perform. They are not a $1000 scope but you also are not paying $1000. Here are some of the threads that helped me make the decision to give them a try.
FYI a BOX Test if you do not know is this:
Put up a target that has no holes in it. Larger the better. Put a single dot in the center of it.
Shoot 1 round at the center,
Adjust scope 5moa up and 5moa left, shoot one round.
Adjust scope 10moa down, shoot one round
Adjust scope 10moa right, shoot one round
Adjust scope 10moa up, shoot one round
Adjust scope 5moa down and 5moa left, shoot one round.
http://weww.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1529770&page=all
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1676026
To be honest I did find a negative post and I am sure I could find a dozen more but I read this one so I will throw it up here too.
http://w.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1795810
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2851237
I first started looking at the Muellers based on these two reviews. They are for older model scopes but they helped with my decision on quality. I wanted the adjustable Parallax - the first one didn't offer it. I didn't need the illuminated rectiles - second one. The model Muller puts out now was spot on for what I wanted.
http://www.snipercentral.com/muellertac.htm
http://www.snipercentral.com/muellertac2.htm
Whatever decision you make you will be pleased I am sure. All of the scopes mentioned are a great step up from what you are currently using. I might also suggest if you go with the Bushnell Elite try and stick to the 3000 series and higher. I have read a number of times that at the 3000 series the quality takes a big jump up. I have only handled and used the Elite 3200 10x and it was excellent but just didn't look right on the old Mauser I put it on