I mention BreezeBrowser as an initial editor. (Editing in the choose the good and bad; and, move stuff around.) IMatch is used for the databasing of what is saved, as it is a little slower in acquiring. And, yes, I too have been using DL Pro since its inception.
Different strokes, I guess. I use IMatch for browsing as the very first step after downloading with Downloader Pro. Its so much more than just a DAM tool. Here's my IMatch flow following a shoot -
1. I make an initial pass through my downloaded images in slide show mode (manual steps) and bookmark keepers.
2. Out of slide show; filter to show non-bookmarks; delete
3. Turn off filter (to see all keepers); select all; delete bookmarks
4. Another pass through slide show, this time bookmarking those I want to work with right now
5. Out of slide show; filter for bookmarked images; voila - the ones I want to do more with
6. Send this bunch off to NX2 via my IMatch interface
Steps 1-5 usually take me about 5 minutes (more "think" time than waiting on IMatch) for a normal day's shoot of about 100 images. I shoot RAW only and IMatch provides an instant full screen visual in the slide show mode which allowed me to stop doing RAW + JPEG. Further the "side-by-side" comparison mode for up to 4 images is great when trying to decide among several similar shots. Although I do most of want I want in screening just with bookmarks, there are also five label colors and 0-5 star ratings when fine tuning is needed.
Bottom line - for me, IMatch as a browser is just as important as its more obvious DAM role. It's probably my lack of understanding, but I can't imagine what any "pure browser" could add. Like I said - different strokes, but want to clarify for those not familiar with IMatch that it is far more than a data base program. As another example, it even provides basic editing features. Lastly, I have no speed issues with IMatch - but of course that depends on lots of things. 200K+ indexed/categorized images in the DB.
Returning to the OP - even as gifted as Mike is, I'd be surprised if the effort to introduce yet another browser/organizer into this market would be worthwhile. It would be difficult to get folks like me (or the Lightroom crowd) to shift without some whiz-bang pain free feature that would automatically move everything we have from our current solution to something new and untried. Browser/organizer is basic fundamental infrastructure stuff. It's not like trying out a new noise elimination program that you can try & toss in a few minutes.