As Phoenix users know it.
So Phoenix users have a new message on their login screen warning them that SSA will make Phoenix all but usable in the very near future. Just to be clear, to the best of my knowledge Linden Lab will flip the switch on at least one of the RC channels next week, and in the following weeks roll it out to even more of the grid until it is turned on grid wide. At that point anyone not on a capable viewer will not be able to render any avatars, not even their own.
We have been trying to get people to move to Firestorm or any other SSA capable viewer so that the transition was easier. Now I can understand some peoples reluctance to change viewers. I personally hated Firestorm when I first started using it, however now I cannot use any other viewer, including Phoenix, comfortably. Yes it is different, yes it will take some getting used to. It does however have almost all of the features that were in Phoenix, plus some that Phoenix never did.
If you are one of those people who choose to use or at least try Firestorm there is help available. To start with there is the Wiki which has pretty much everything you need to know about the viewer. We also have classes that cover the preferences, menus and some of the more advanced features. There are also the inworld help groups where you can ask for help. (of course there is chat lag to deal with there)