If you look for something real efficient, then check ACDSee's Pro 3. I know that ACDS had some problems with former versions, but the Pro version 3 was stable right from the start (even in Beta). It's for quite some time on the market now, and I use it among other pros for my daily work.
Not just for tagging, etc. but even for editing and retouching. Version 3 has a complete revised GUI with an build in workflow for photographers. It's rated as the best alternative to Lightroom and cost a fraction of the price.
ACDS offers even a 30 day fully functional trial version. No watermark or anything else set during trial. Just use it and if you like it, then buy it after 30 days (or earlier). I was Beta tester for both (Lightroom & ACDSee Pro) and ACDS simply has (in my opinion) the better GUI, flow and a few perks that Adobe doesn't offer.
PS plug-ins are not supported, but any image editing software can be set up within ACDS Pro 3 as an external editor. In my situation, most of the retouching is done even in ACDS Pro 3. If I really need a plug-in, I simply go from within ACDS to PS / PSE, do my filtering, and leaving PS leads me right away back to ACDS where I was before. Saves me a lot of time compared with PS / PSE only.
I'm NOT paid by ACDSee for telling this. Nevertheless, I was so pleased with the product that I became an affiliate myself. I use their Pro 3 (no other version) extensively 'in the field' and never looked back to LR again.