Rated 2 out of 5 stars

Its ok, but it doesn't have THE most important (to me) function.
Need to be able to apply a new and.or existing filter to ALL Email Accounts.
Either by merging to another account (removing the "To: criteria), or by selecting the INBOX (unified inbox) as the folder to filter when creating or editing a filter. I would gladly pay for this filter function.
Also it would be good to be able to select multiple templates when creating filters, such as "From" AND "Subject" not just one or the other.
This addon does not really save very much time, if like myself, you are already proficient at creating the filters. Sorry to bring down the vibe...but

This review is for a previous version of the add-on (2.8). 

Thunderbird, SeaMonkey and Postbox store and manage filters *per account*. This is by design and cannot be changed by a lowly add-on, so I am afraid you are asking for something impossible. Merging filters so they apply to more than one account simply cannot be done under the current filter architecture. So the 2 star rating won't change that or help.

As regards your other feature request, check out this bug:
https://www.mozdev.org/bugs/show_bug.cgi?id=25989 "Allow creation of Custom Templates"
This feature will allow you to create templates with more complex pre-filled rules. It is much more difficult to explain than to use, please give it a try here: http://i.imgur.com/NEycbEk.png

Also this is not the right place for feature requests; please add them here:
http://quickfilters.mozdev.org/bugs.html

As regards saving time, the main reason qF was initially implemented was to deal with an ever growing folder tree - the autoselect target folder was the biggest pain when it used to force us to scroll through 500+ folders. Also if you have more than 100 filters the search functions I added become more important; give them a try some times. You can right-click any folder in the tree and investigate whether it is targeted by a filter. You can find filters that do the same (duplicate search) and you can search for filters by condition, tag and (reply with) template.