1) Edits to the original post are not reflected in the search indexing. This means you'll frequently have threads appear that once had the item you need, but no longer do. It also means that, if you make a typo in your OP or neglect to add relevant search terms, you should just make a whole new thread rather than correct it.
2) The sort order is by the original post date. This means an older thread, even if it's still being updated and bumped by the original poster, will be essentially invisible. This heavily incentivizes people to keep making new threads so that they'll appear in search results, further increasing spam and punishing people who "play by the rules".
Would really love to see both of those things fixed. Hell, hire me, I bet I could figure it out, I used to do a lot of database stuff.