My highest scores for Spider Solitaire (Windows 7's version) on intermediate are as follows:
1238 (5/23/2010)
1222 (6/20/2010)
1214 (8/30/2010)
1195 (4/4/2011)
1180 (6/12/2011)
I'm positive there are higher scores possible. :)
Wikipedia states that the highest possible score is 1293 given a perfect deal (and I'm assuming that's on Expert mode given the additional score possibilites being lower than what I've achieved on intermediate mode).
Win percentage is almost meaningless (addressing another "answer") as all games of Spider Solitaire are winnable given the unlimited undo's in Windows' version. I've played 646 games thus far with a 100% win percentage.
Wikipedia link: http://en.wikipedia.org/wiki/Spider_Solitaire_(Windows)#Highest_Possible_Scores