Developer reply by Krzysiek Wróblewski
Rated 4 out of 5 stars
There are still problems with the priority selector in Compose mail window in Glasser 0.4.
http://img510.imageshack.us/img510/1633/tbglasser.png
Should be finally fixed in 0.4.1 ;)
To create your own collections, you must have a Mozilla Add-ons account.