Rated 5 out of 5 stars
Very good so far. I love the restartless addons, when I can get them.
I'd love to see a full set of options for faking agent strings for preset lists of sites, with wildcard matching. (Including '.*' for all sites not matched with narrower filters.)
I haven't tested yet to see if this also changes agent strings reported via JS. If so, that would put this far ahead of the old User Agent Switcher addon.