Fitted Mesh is here - which is a good thing, however it seem that a large percentage of people on SL are currently stuck using the most popular viewer on the grid, Firestorm.
I wont got in to the details, but I will give the facts.
Firestorm does not support Fitted Mesh at this time and after struggling to find when they will, it seems users will have to wait until near enough the middle of March to be able to view this officially released functionality.
Fitted Mesh was released on the 10th Feb by Linden Lab and builders like myself are creating items in fitted mesh. If you are using Firestorm, you will not see these fitted mesh items as they are supposed to be seen - in fact you will just see a mess on your screen.
To that end, in order to help customers see what is currently going on in SL, I have compiled a list of Third Party Viewers that are capable of viewing Fitted Mesh.
The Official Linden Lab Viewer
As you would expect, the official viewer is quite happy handling fitted mesh. It doesnt have all the extras and features you find on a Third Party Viewer, but it does work. Downloads are obviously on the official Second Life Website.
Singularity (for those that like classic SL viewing)
Viewer 1 today is considered to be old hat, and sooo 2008. However it may surprise you to know there is still a Viewer 1 Third Party Viewer out there, and its good enough to actually be my personal Primary Viewer of choice. Its fast (running circles around viewer 3), stable, has all the classic Edit appearance systems (faster building), and features virtually all current SL functionality and features, as well as loads of handy tools and gadgets. And it featured Fitted Mesh support even before the official release.
If you like uncluttered, clean viewing, which offers excellent FPS rates and 98% of the tools you are used to, this is the viewer you want.
Kokua will be better known from some years back as Imprudence however Kokua is based on Viewer 3 specs. While not stuffed to the max with tools and features, Kokua is more advanced than the SL viewer, and offers fitted Mesh support. I have Kokua installed on my system and its not bad, if a little basic.
From here, as mentioned Firestorm will eventually get Fitted Mesh support but it wont be for some time.
Of the other viewers out there, Both Exodus and Catznip seem to be defunct projects at the moment with no movement on those since autumn last year. That may change and if it does I will list them, however at this time neither support fitted mesh.
All of these Viewer above are officially listed in the Linden Lab Third Party Viewer Directory.
It would be wise to use that list - using any other viewer is a risk not really worth taking.