I got to test this out on my home connection tonight and overall my conclusion is that it worked about as well as it did from the faster connection at work. My home internet is through Comcast cable; I think it is supposed to be 15Mbps down though honestly I'm not even sure anymore. I did tests against servers on both coasts and got download speeds of 4-9Mbps with latency in the 40-70ms range, and to Denver it was 15-20Mbps with 15-20ms latency.
On this one I tried out Dirt 2 since that is a game I have played for hours and hours on my PC and I wanted to see how it compared. Visually there was still a bit of indistinct graininess to the image, especially around things like UI text and such. It wasn't too bad, but it just didn't have the crispness of what I am used to. That may be lessened when looking at a TV screen that is ~8 feet away, and not a monitor 2 feet away.
I did have one network hiccup while playing, and during that time the game briefly paused and then there was significant graphic tiling for a second or so after it restarted. Not a huge deal, but worth mentioning.
As for controls and lag, I would say for the two games I played it was hardly noticeable at all and I was able to quickly make a mental adjustment to it. In Dirt I got 3rd place in my first race and won the second one, so there ya go.
Personally I probably will only use this service as a free 30 minute game demo station, but if I had an older PC or really wanted to play games on my TV I'd certainly consider the micro console or just playing games on a crappy PC that it couldn't normally handle. I'd say if you're interested it's definitely worth a try since there's no subscription fee and you can try any game free for 30 minutes. The biggest problem, I think, will be trusting that the service will be around for as long as you want to play your games, as well as having competitive prices.