It's a Netflix-type streaming service for Warners' classic movies — all the old WB, MGM/UA, and RKO films owned by the studio. So basically, TCM on demand, with a lot of HD content.
I was trawling through the app store this evening and found that they had a version up for the iPad. It's $9.99 a month, but there's a free two-week trial period. I'd really be interested if there was an Apple TV channel, but so far set-top box support is limited to Roku.