I use Windows Explorer all the time (Win7) because, well, first I've been using it for all these years, since Windows first came out with an explorer, don't ask me which year!
But I don't mind using it because it's fine for browsing for any anything and everything. I have my folder/files set up so that I can easily look for whatever, whether it be jpegs I've exported for the Web, or movies I want to watch, or documents I've been working on, whatever, stuff that won't show up in Bridge or Lightroom, but I have quick access to them. And I can do whatever I want with them, whether it be to back them up, delete them, copy or move them, easy stuff.
For images, though, that is for my "working" Library images, I pretty much stick to Lightroom because LR integrates all the things I want/need to do with those images/files. For those, I don't want or need another browser, and in fact, without some special software the Windows Explorer can't "see" the jpeg images embedded in Raw files and so I just don't bother. For jpegs that I've exported for the Web or other uses, yeah, I use Explorer, it sees the thumbnails and is functional. Lightroom doesn't "see" the jpegs, so it's a no-brainer to just switch to Explorer for such things.