Oh! You're welcome to comment any time - I always find time for LJ - it's my only outlet for socializing really =)
Let me see - it probably depends a lot on what type of paints you are using. I work exclusively in acrylics, and I've found that once you get used to a texturized surface (which takes a little getting used to!) it is far superior to painting on paper. You don't have to worry about weighing the surface down with too much paint, or having the paper get degraded by too much water, or anything like that since it's a lot more substantial!
One of the first things I do when I start a painting on canvas is that I do one or two full coats of whatever the primary background colour will be (in my case, usually black). I do this to make sure that I have a fully opaque starting point, and that there is no white grain showing through. I apply it fairly thick too, which smoothes down the surface somewhat.
Very true - it's hard to erase on canvas! Whenever I change my mind about something, rather than trying to erase, I simply paint over. I try to keep as little impasto (bumpiness in the paint) as possible, so if I need to paint it over it will go smoothly. Some paints are more opaque/transparent than others, so you'll probably have to do some experimenting with your own paints to see which ones cover better than others.
Hope that helps! If you decide you don't like canvas, there are some other good options other than paper - masonite is neat stuff - it's like a very dense heavy board that has a perfectly smooth surface. Primed wooden panels are good too - another very smooth surface. They sometimes have a more pleasing "finish" since there is no texture from the grain (like a canvas), so if canvas doesn't seem to work for you, those are good choices as well =) http://www.dickblick.com
are great sources for all of that stuff! (And for canvas pads and stretched canvases!).