1. Not related to the update, but to start things off, requiring registration to *read* forums for a game is just . . . .well, it's either silly or amazingly paranoid. To post to a forum, yes, registration should be mandatory. To read, no.
2. You killed off my savegames! Thanks for that, really. DoW2 is fun, but I'm honestly not sure it is "replay the same missions over again just to get back to where I was" fun. I have a limited amount of gaming time available, and I don't appreciate being forced to choose between abandoning the campaign or playing through a bunch of missions I've already done. To the inevitable "suck it up, no TRUE gamer. . . ." yadda yadda fanboy responses this complaint tends to generate, I can only say to such responders that I admire your ability to view mindless repetition as entertainment, but I do not share it. Would you like someone to "update" a multi-hour tabletop boardgame you had been playing by flipping the table? After all, you are being afforded the opportunity to rediscover the content!
3. "But wait!" you say. "Now you have multiplayer without Games for Windows Live!" -- Fair point, from all my interactions with it so far, I can agree that G4WL generally sucks. However, you've also removed LAN play, and this ticks me off, as LAN play would have been the only way I would be likely to have played this game multiplayer. I have no interest in joining up with some random person on the interwebs to play the game -- I prefer to play with my own, actual friends and family, and would prefer NOT to have to rely on the internet to do so. This was possible previously, but no longer.
4. Steam really shares a lot of the blame here -- they should have provided a way to make your "update" optional for those of us who didn't need/want it yet. I would have been very happy playing DOW2 offline, in single player, and updating later at a time of my own choosing if Steam had offered such an option. I would have still been irritated about the loss of LAN support, but the savegame thing would have been a non-issue.
In conclusion: Bummer, dudes. In my fairly lengthy history of gaming, I haven't seen too many updates that removed more features than they added. Congrats on saving internet multiplayer, I guess -- I'm sure lots of folks are happy about that, but for me, it was really a "table-flipping" experience.