I've played a couple games today, and I am very impressed with this new patch. From what I can tell it has greatly reduced the lag. Lag is still possible, but just not as common and nowhere near as bad as it was before.
It's a shame that we didn't have it two years ago, but it's very good news that it's available now for us to enjoy and for testing and further tweaking before Rebellion comes out. It fixes what I think is the biggest complaint people had about online multiplayer. The online multiplayer user interface could certainly be improved and could use some additional features, but with this lag fix it almost feels as though it's polished.
If the online multiplayer in its current state had been this way when the original game was released back in early 2008, I bet we'd have far more players online today than we do now. (I'm not talking about the content of the expansions, but things like the ability to host games, minidumps, desyncs, lag, etc.)
This patch has really increased my enthusiasm for Rebellion. I almost view Rebellion as a Sins-2 since it will be a stand-alone game. It sure would be nice if the sequel to an all-time favorite game of mine were actually an improvement over its predecessors (as opposed to being a major disappointment that kills the game's franchise).