I know that this is jumping the gun slightly as it is early days but has anyone got any information on how we can build apps that take advantage of a basic local SQL database like you used(!) to in Windows CE/mobile 6.x? I can't find any info on the intertubes so maybe it hasn't been announced yet??
Is ErikEJ hints at, sql is on the device and is used by the built-in applications and OS ... however it's not exposed. If you watch one of Charlie Kindel's talks at MIX10 and keep watching for the questions at the end he mentions this. He hints that it's something that they want to look at exposing in the future, but they didn't have enough time to do so in this release.
Anyways, unless you live/work in a place with spotty coverage, I think that the device will have connectivity more often than not. Because the user will either be in wifi range, or on the 3g network. I know that it's very rare that my iPhone doesn't have data connectivity. So you can probably rely on having access to a cloud service somewhere.