Today, at that Avenue A | Razorfish event (A A|R is owned by Microsoft, it turns out) there was a presentation from the people who built two different sites for XM Radio. The Online Store was built with Flex, the XM Program Guide with Ajax. They both look pretty good. I guess it means you can’t sign up for XM with an iPhone. I remain unconvinced that the extra sizzle and flash you get with RIA technology is enough better than Ajax to make it worthwhile—but then XM reported increased conversion rates when they rolled in the new site. Interestingly, they said that Ajax was a particularly good fit for the channel guide because HTML naturally handles grid-like structures well. True when you think of it, but I never had.