I've been learning how to create Mesh objects for a couple months now and by jove it's not easy.
The creative side is ok, it's just the technical side is SO fragmented and this is NOT Linden Labs fault. The 3D modelling world as a whole is a nerdy one and is no way in a position for mass uptake by the general public.
You have major 3D package software that i cant afford to use, so cant comment on wether Z-brush, 3Dstudio max or what ever else has a more complete and user friendly work flow. For the Mac there is also cheaper solutions such as Silo and AC3D to consider but the majority of newbs to Mesh will no doubt find their way to Blenderas its FREE.
The problem with Blender though is its currently very slowly going through a transition of being ridiculously lousy with UI (2.49) to a more intuitive easy to use UI (2.5). I found it easier to get to grips with Blender 2.5, thats the whole point of Blender 2.5 but when it comes to using it for making SL Mesh you will soon discover vital features that make Mesh easier and more efficient are strewn between the two version of Blender making it a very frustrating experience to learn. Although it is free and they guys working on it are doing it out of their own pockets and through donations so Kudos for them really....... just wish they worked quicker to implement the missing features :-p
I have found that to make a good prim efficient Mesh for SL, i have to use multiple applications, porting from one to the other. These 3D apps do not seem to have all in one. Some Like Silo don't even support the Collada format, others lack Poly reduction, and whats worst is that these programs have been around for years.
So anyway, if you are thinking of making Mesh in Second life, i have made a list of subjects i've had to learn regardless of which 3D software i've been using.
1. Learn how to create Mesh objects, learn about extrude, vertices, faces, edges and manipulating them.
2. Learn about subdividing and modifying.
3. learn about unwrapping UV's, texturing & multiple faces.
4. Learn about Levels Of Detail (LOD) and how to decimate/reduce faces on your model.
5. Learn how to weight your Mesh and rig it for wearing.
6. Learn about Mesh Physics and how to apply it to your mesh.
7. Learn How to use the SL Mesh Uploader and how it deals with LOD and Physics
8. Learn how to keep Prim Equivalence LOW. (not as easy as you may think)
Lets not delude any SL users here, it's not as simple as rezzing a prim, texturing and linking , you really do have to learn 3D video game modelling. There are university courses lasting two years teaching the stuff you have to learn here. But there are some amazing talented and generous Users in SL who have given me a lot of help and advice to learn on the SL Forums.
Those who think Mesh would replace the old Plywood Prim are utterly mistaken. Even Scultpies and Mega prims will be useful in the fight for prim reduction since Mesh Prim equivalence will increase along with a Meshes size.
The world of the Tiny will be cost a lot less than full sized Avatars.
So give Mesh a go, and do so now before it goes onto the main grid, as right now you dont have to pay for mistakes ;)