HDMI has a few new features but mostly are video improvements except for the HD audio bitstreams for the audio side of improved features. AS stated before though it will not work with movies encoded in advanced mode, only basic mode encoded discs.
A couple of the video improvements are:
1. DeepColor support, but there are no displays available now or even announced that can do this yet. Then there is the issue with finding a source that is encoded for DeepColor. There is currently no source either so this is probably a feature that will not do a damn thing until maybe 5-10 years down the road. Neither HD disc format has DeepColor support.
2. Lip-sync correction seems to have some use, but ALL devices in the chain must have HDMI 1.3 to use this. It would be very expensive to replace all equipment in the chain just for this improvement. Currently there are no displays with a HDMI 1.3 input AFAIK, so this isn't available yet either.
I think HDMI 1.3 is great but it is still way to early to be trying to get it unless there is little to no extra cost to get it IMO. It will be years before any real world uses will make it worth paying more for. Chances are most devices will already be replaced when most improvements come online. IMHO