2.8.1 is OK. With 2.9.0, X fails to start because it says it was unable to detect that any monitor is connected (and presumably therefore does not know the resolution) and finally "screens found but none have a usable configuration." I have the last-generation Mac Mini with Intel graphics and Core 2 Duo 1.86 GHz, and a Dell 2405 DVI monitor connected.
emerge -vp xorg-server
Please file a bug in FreeDesktop's bugzilla  so that Intel developers can properly fix this bug. Please paste the url here.