One complaint I've had with the beta thus far (and it's entirely superficial) is the way thy've altered the coloring of the map originally shown at E307 (a portion of the map makes up the Blood Gulch mutiplayer level). It's as if they listened to all the haters and added in a bit more color, thus taking away it's awesome contrast. The sky is much darker, more like night, rather than like an ominous storm cloud. Aside form the sky, the level in general seems to be brighter, and less subdued. I'm hoping they just did this for multiplayer.
Here's a shot of the original version of the level:
Compared to this:
I know it's hard to understand what I mean when looking at these two shots, but I preferred the style in the upper picture more.
Here's another look at the original version:
The general look of the square is cooler, imo, and the other areas of the level are darker in this video, allowing the lighting from gunshots to stand out more.
Of course, they could've just changed this for multiplayer to make it easier for each team to see.