I use them in a few forums, specifically my "Buy, Sell, Trade" forum where prefixes provide an easy way to see the transaction type being posted.
Looking to pay to have the IPB import script modified to include an extra "prefix step" added to the import process as follows:
1. Identify source thread prefixes and the forums they're applied to,
2. Recreate existing prefixes during the import process,
3. Allocate each prefix to either a designated forum or global (user input if necessary),
4. Attach the appropriate prefix to applicable threads.
Not sure what I should do from here - ask for PMs or replies to this thread? Either way, it's the last issue that's current;y preventing me from switching and I'm sure it would be useful to other potential IPB converts as well.