Given the importance of the modding scene to Bethesda games, having the backing of NexusMods and their Nexus Mod Manager software was always going to be handy. It was never in doubt, of course, but the fact that Fallout 4 is now officially supported is worth knowing.
Before you jump in and start downloading all the things, however, it's worth noting that many early mods are likely to be problematic and could result in some unfortunate issues. Back up your save files just in case people!
Alternatively, everyone could wait for Bethesda to release the Garden of Eden Creation Kit (GECK) next year. There's also Mod Organizer if you want to go down that route, which some prefer over NMM.