Hi Luke,
Thanks for your question! The answer is simple, but in part, unsatisfying. Weblogs are now called Channels in EE2, and the upgrade process will automatically convert all weblog references to channels, so there’s no need to worry with that.
Regarding the Photo Gallery module, on the other hand, we do not currently have an upgrade path for EE1 Photo Gallery users. We’re not abandoning it, to be sure. It’s just undergoing a radical change from EE1, and it’s just not yet available.
If you rely heavily on the Photo Gallery module, it may be best to stick with EE1 until we have an upgrade path in place.