Opaque as a glass of bromine mixed with ground asphalt. Even with the beta->release UI improvements [color=grey](mostly with economy display, but also actually showing unit damage and weapon types)[/color] it's damn near impossible to tell what your units will do, let alone the opponent's. "Effective against X" doesn't help me when everything seems to be effective against at least two categories of enemies, so knowing which is more effective is a PITA to work out.
There were also issues in beta with powerful generalist vehicles [color=grey](US Stryker MGS, Chimera Terminator, Cartel Otomatic)[/color] that just dominated everything, but I don't know how that is now, since balance has been adjusted quite a bit. I'm glad they reduced the sheer absurdity of capture rushes, but given that those dominated in beta when the generalists didn't, I have no idea how well the fundamental design even holds up [color=grey](i.e. assuming perfect balance)[/color].
The maps being so large with unit sight ranges being so small also doesn't help, since it can often feel [color=grey](at least in the early game)[/color] like there isn't even an opponent.
Overall, I'm not sure what Eugen was trying to do. Supposedly recapturing the magic of Command & Conquer: Generals, but that game was relatively straightforward in both what you could build, and what they would do, especially since C&C:Generals didn't have half a dozen units per production building with 2-3 role-changing [color=grey](or at least generalizing)[/color] upgrades each. Mind you, I've personally come to dislike upgrades, especially tech-tree bottleneck upgrades [color=grey](not including Zerg/WarCraft main building upgrades, that upgraded building can be destroyed to remove it. Also, Rise of Legends and Rise of Nations both charm me enough to look past it in that case)[/color], since they are non-interactive compared to on-map options.
Oh yeah, graphics. Normally I love maxing out all graphics settings and making everything pretty, but that just gave me a headache here. I had to turn down terrain and foliage detail to near minimum just to be able to pick out units, not to mention the headaches I got from moving the camera around. The camera also seemed noticeably choppier at higher terrain detail, but I'm not sure if that is my GPU fillrate or texture sampling speed, the GPU<->RAM texture data transfer, or a hardware-independent issue with how the engine loads terrain textures.