I started a 3g o my desk at work in early May and it's pretty awesome. I've got the Marineland AIO 3g from amazon with a few mods:
1) swapped out the return pump for an aquatop102 and have it running full speed (130gph)
2) took the media basket out and put chaeto in the rear.
3) cut off the stock light from it's hanger and cut a hole in the lid to the back chamber so I have the stock light (9w) lighting the back chamber 24/7
I do two 2 gallon water changes a week and feed m/w/f. I've got a fire shrimp/yellowtail damsel/1 blue hermit/1 nerite/1 margarita. Takes me about 15 mins to brush the corners, sand threshold, blow the rocks, vacuum the sand and replace the water. Could probably do it faster but I enjoy it so I take my time.
I keep the lid on it just so no one will come by and drop something in it. I've got a ABI Blue Tuna 12w Par38 bump 15" from the water and am growing duncans, frogspawn and a handful of sps. Ducan is growing 3 more heads and frogspawn is splitting, just noticed the 2nd mouth today actually.
It's especially serene when I'm getting screamed at by a customer on the phone, ha.