Nope, not yet. So far I've only visited two 'settlements' near the starting area, plus the starting town, as well as some random exploration in between those areas. The factions I've encountered so far are the neutral inhabitants of two settlements, a group called the Powder Gangers, and a few NCR Army types. Seeing the NCR again is pretty nice, and it helps make the game feel a lot more connected to the world of FO1/2. The Brotherhood of Steel never really felt right in FO3 due to their location, but NCR fits in perfectly in New Vegas. I've also met several people from The Hub, which is another nice shout-out to the originals. Oh, and I've made Healing Powder out of the same ingrediants needed to make it in FO2. It's little stuff like that that makes New Vegas seem to fit better into the FO1/2 world than FO3 did.