As Blizzard outlined in the past, the new 1.0.8 update for Diablo III is multiplayer-centric, bringing enhancements like Magic and Gold find bonuses for having more players and notifications for Elite monster encounters.
There are also some minor fixes, like achievement bugs, as well as some major Battle.net tweaks, like improved matchmaking tags, and social (friend list) features. Classes also had some tweaking, with pretty much every character in the game getting some sort of buff. You should also encounter more monsters in Inferno mode as a general rule.
But all of these minor tweaks pale in comparison to the core of the update, which makes monsters easier in multiplayer games than they were before, to help facilitate more co-op play, rather than supporting the "playing solo to min-max" mentality.
I really enjoyed my time with Diablo III, but this isn't enough to get me back in the fray yet. I already played every class in the game a fair bit, and all of my friends have moved away to other games in disgust of the Real Money Auction House. Hopefully there will be some content patching in the near future, and if not, there's always the next expansion.
Patch 1.0.8 [Blizzard]