I have always hated the standard builder-grade baseboards in our home. They are so small and puny. I have considered replacing them with something taller or just cheating with something like this. I still haven't decided what I want to do, but we had to remove some baseboard for our home office built-ins, and it was so easy that now I'm not so scared of the idea of completely removing some of our puny baseboards.
Here's the very simply process I used to remove our existing baseboards:
1. (Optional) If you only need to remove a section of your baseboard, use a Dremel Multi-Max - type tool to cut your baseboard. I didn't get a picture of this step, but you basically start in the vertical center of the baseboard and carefully cut up and down until you clear the top and bottom of the baseboard. Be very careful near the bottom that you don't damage your floor.
2. Use a box cutter to slice the caulking along the top of the baseboard. This will help minimize the amount of wall board that comes off with the baseboard.
3. Shove a metal putty knife between the top of the baseboard and the wall. Then use a pry bar to pull the baseboard off. Keep the putty knife behind the baseboard to keep it out from the wall and just slide it along as you go with the pry bar.
4. (Optional) Because of the height of our hardwood floors, I had to use the putty knife/pry bar method vertically as well to lift the baseboard up over the hardwood.
Voila! Now you have a bare wall to add fancy new baseboard.