I’m not very experimented with the Blender sculpt mode as it requires too much poly for my system when i want to make good details, i am more an user of Sculptris as when it comes to sculpting.
Sculptris allows me the possibility to make high level of detailing for much much overall less faces required than with Blender multires system due to the specific “create face only where you’re need them” method Sculptris is using.
But for both application, i always found more easier to sculpt when you have a base shape than to sculpt from a default sphere/cube/mesh, because you can then focus more on the details than trying to give it a shape.
By example, using Blender 2.57b, i use this squirrel picture took from a quick google search :
And build a simple base shape roughly looking like this picture.
After a few multires level i can get something a bit more looking like a squirrel :
I’m sure with a better base shape it must be easier (though i think it would be even easier with Sculptris).