I get seed potatoes from Seeds Of Change, which are expensive but they have good ones. Last year I did Cranberry Red, German Butterball, Viking Blue and Peruvian All-Blue. Planted in late spring due to a horrible snowstorm in April.
We had a miserable drought through August and I don't water my garden at all because, um, basically I'm lazy. No, no, I was trying to conserve water and save the planet and stuff! Yeah, that's it! Not lazy at all.
They all did OK, but the Peruvian All-Blue ones did AWESOME. Lots and lots of potatoes, a huge basket of 'em. Will definitely get some more next year. The only downside, while they make wonderful mashed potatoes, the lovely shade of purple is a little weird on the Thanksgiving table. Maybe they'd be better as whipped potatoes for Easter?