I don't really use mine for anything like you would use it for but I'll offer whatever help I can.
You ask about multiple work spaces. Is Spaces not what you're looking for (i.e. multiple desktops)?
For uninstalling you can just delete apps, but that doesn't always get rid of everything so I suggest using AppDelete. I have a feeling it is just a choice over AppTrap that sj linked to...I don't know which is better but I know I like AppDelete.
I also suggest getting OmniDiskSweeper (I didn't pay for it, just stick with the free version). It's a great app for figuring out where most of your hard drive space is being used. All of the OmniGroup apps I've used are nice, but I haven't felt the urge to pay for any of them.
That's all for now, gonna go eat lunch.