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!