I went to the 2 year anniversary party for the Imprudence Viewer today. If you didn't know that it's been around for 2 years...well, you're not the only one. I had no idea. But 2 years ago, third party viewers barely mattered to me at all.
I use the 2.1 beta viewer from Linden Lab pretty much exclusively these days, as I've mentioned before. But if I were going to move to a third party viewer, Imprudence would be the one I would use. Although I used Emerald and liked it, I never fully trusted it. Same with most any of the others I tried as well. When I originally started Second Life, we had one viewer [sometimes 2 if you used the Release Candidate], and that's what you used. Didn't work for you? You either made it work by upgrading your stuff, spent less time in SL, or you sat around in your skybox IMing with friends and waiting for the next viewer release. When the third party viewers started coming out, I thought it was kind of cool, but at the same time, I didn't quite trust them. Who WERE these people making them? What risk was I taking every time I put in my password?
But, I trust Imprudence. I know some of the people behind it, and one of them I trust very much. So when the day comes that they put in some very important features that SL viewer 2.1 has that I have grown spoiled with, I will most definitely be using Imprudence more. I can't promise to use it all the time, but I promise to use it more. :)