Most important change: latest stable version is in stable branch now, latest development version is in default branch. So to get the latest stable code, type:
hg pull hg up stableAnd, since this step is done, nightly builds are now always built from the stable branch - i.e. there are no any severe changes like new features, but only bugfixes, new samples and possibly, improved helpers (like DisconnectedResult, that will be improved and moved to Xtensive.Storage later).
So in short, from this moment it's much safer to use nighly builds: they are at least as stable as the latest release.