Played around with Mavericks this morning, its really Lion Part III as expected, although I dont think its as big an update as Mountain Lion was from Lion.
Overall, seems pretty stable.
Grey linen seems to be gone completely the login screen in particular looks really plain and ugly without it.
Pretty much all the goofy looking apps have been changed other than Game Center. Notes looks off without the lined yellow paper. Hopefully these apps will change over the course of the beta.
The dock looks shit when moved on to the left hand side. Hopefully a plist/tweak can change this.
iBooks isnt in this beta.
Maps is pretty plain, was hoping for a better way to flag wrong info, but its the same report a problem system from iOS
Overall, seems pretty stable, but nothing that makes me want to make it my main OS right now.
Wait what did they change about the dock? Left side dock is the best