Essential addon, should be built into FF. Works perfectly for google search results for doc*, xls*, ppt. Test by doing a google search for "Best filetype:xlsx", rightclick the icon to open in new tab. Keeps original page title, is session persistent.
Limitations (Otherwise would be 5 stars):
1. problems with different link formats (Firefox user 14393471 below), eg the icon appeared on a link which was a graphic, but it seemed to be over-ridden by the graphic link, hovering couldn't get the "open this...file" popup to appear. (placement issue? fixable by right click menu item as a backup to the icons. At least it found the link - 2 other addons didn't) .
2. Description needs updating: uses ms view app; no toolbar icon or options; doesn't find pdf (not necessary - FF does) or csv; cannot preview local PC files (they have to be on the net).