I find that white-fleshed sweet potatoes are delicious (this is coming essentially from a monk, mind you) when cut about 3/4cm thick and microwaved for about 8 minutes per plate. This is pretty much the only way I eat tubers. Have to find the right variety, though. They're usually called Japanese or Oriental sweet potatoes. I've tried this with standard potatoes and even I thought it was a bit too bland.
Am I the only one who thinks potatoes are a total waste of calories? I'd much rather down some green veggies or meat... even dousing them with butter can't make up for the blah-ness!
I also eat potatoes with low-fat condiments like tomato paste, or I'll mash up roasted garlic and basil (much lower fat than pesto) or other herbs to put on top. Or crack a soft-boiled egg over them. I actually prefer all those things to eating potatoes with butter (which I find makes it too easy to overeat.)