Vendors usually sell Malaysian and Swahala driftwood for 2 reasons. 1) They sink (if not immediately, eventually). 2) They are fairly non-reactive. Though they do reduce pH, they usually do not flake off and cause big problems.
If you're stressed by the price of the stuff at the
LFS, check out ebay. There are some nice pieces on there for less than you'd be paying locally.
I'd be a bit wary of using driftwood that you've collected in your tank. You never know what chemicals have leached into it, and what organisms are living in it. I know boiling will no some good, but I prefer peace of mind!
