IM is ImageMagick
well pretty much the compare between the products is still the same. http://www.photopost.com/compare.html
Now yes uniform thumbnails are exactly what you think.
Here is the announcement thread about 6.0 it has what things Michael added. http://www.photopost.com/forum/showt...21#post1204921
The more ajax is most of the showphoto actions have been added into the ajax.