As much as I use different viewers, I miss lots of the problems. Lance Corrimal, the Dolphin Viewer person, pointed out some of the problems in SL Viewer 3.x. There are a couple of gotcha’s.
SL Viewer 3 and viewers based on version 3.x code are slow. I’ve been using the SL Development Viewer for so long I expect it to be slow. If you are just moving to a 3.x based viewer… well prepare yourself. It affects the SL Viewer and third party viewers based on version 3 code.
We usually see these problems manifesting as problems with alpha layers. If you are wearing multiple layers then an outfit replacement only replaces one layer. That results in layers left behind from the previous outfit.
A work around is to remove the current outfit then add the new outfit. This does leave you nude for a few seconds. So, you need a changing room… or not, if you are an exhibitionist.
If you attempt to teleport more than one person at a time, you have likely run into this problem. Inviting more than one person to tp crashes the viewer.