For our trip last year, there was a 12% variance in the banks favor for converting us to JA here in the states. The rate was substantially worse than what you get at the airport (which is bad enough itself). I was really surprised at just how bad the rates were.
I don't think we've used travelers checks in a number of years though. We used to get them free, either from American Express or the bank, but the last time I looked into it, the hassle and expense was too much to bother with.