I am back with Google Desktop Search. I was using MSN desktop search but I got tired of it not shutting down with the computer. I have moaned about GDS in the past, particularly that I don't like the idea of results appearing in a web browser because the only thing you can do is open them, you don't have Windows Explorer's right-click context menu. After months of using MSN search I have decided that this is not a big deal: on the whole I can remember where things are and I use salamander to access them, I only use search when I have lost something.
GDS integrates better with thunderbird than MSN search did: I installed an MSN thunderbird plugin but it never worked. GDS supports it out-of-the-box, although as I use IMAP it will only index the messages I actually open, not the 2400 messages in my archives (unless I view them all one at a time).
I have come to appreciate the various plugins available for the GDS sidebar, especially the email preview thing: in fact I find myself reading email on that rather than switching to thunderbird. There are many plugins available but their installation programs often seem excessively large (megabytes) for something that is hosted by another application and appears in a window two inches square.
I have stopped using Opera for now: it's mail reader was not showing me the contents of some messages so I abandoned it. Some emails can crash it and it is still not as compatible with web sites as firefox. It has got me hooked on gestures and I find myself gesturing in FireFox to no avail (except at microsoft.com). I have installed a gesture extension and am hoping the next point release of firefox doesn't break it.
Twitterings

GPSoftware's explorer replacement Directory Opus (gpsoft.com.au) has fantastic find-file functionality, including hooking into Google Desktop Search if its present on your system. This gives _exactly_ the functionality you're looking for here of being able to perform contextual operations on the results. Combined with DOpus' 'collections', you can even have Spotlight-like live-search-result folders.
DOpus isn't free but it's damn inexpensive for what it is and one of the more impressive Windows tools I've seen.