Make no mistake about it: interest-only loans are the hottest thing going in the subprime mortgage market right now. But not everyone is sold on the long-term viability and performance of IOs. According to affiliated newsletter Inside MBS & ABS, $27.82 billion of subprime IO loans were securitized through the end of September, up from just $2.54 billion during the same period in 2003. Putting that into perspective, IO loans accounted for 9.6 percent…