I bought Grey Goo the day after release and it's easily one of the best RTS games I've played since Age of Mythology. I think this might be the first PC game I've paid full price for since Fallout New Vegas and I'm not disappointed, 22 hours in.
Resource management revolves around a single resource that you have to continuously mine from pools which run out over time, forcing you to expand and set up satellite bases.
Base-building varies massively between the three races. The Beta require all of their buildings to be attached to 'hubs' which provide power. The hubs themselves take up a huge amount of space, so building bases can be really frustrating. Human bases are really fun to build and manage, allowing you to build hundreds of defense towers/missile silos and teleport them as your bases expands. The Goo don't have bases as such, but it is really fun to play as them as all of their 'buildings' are completely mobile.
The campaign is excellent but I found the Beta portion extremely difficult, even playing on normal. There are minor frustrations here and there around working out the exact way you're supposed to be executing a mission in order to succeed but overall I really enjoyed the trial-and-error stuff.
It's also worth mentioning that the story and cinematics are some of the best I've seen in an RTS, and it's the kind of game we're rarely given as PC gamers these days. I bought it as much for supporting the devs as I did for how the gameplay looked. It deserves to be successful.
