Based on this part of the Rule: "It is the intent of Rule 10.17(b) that a relief pitcher pitch at least one complete inning or pitch when a crucial out is made," it looks to me that Neshek should not be disqualified due to only pitching 2/3 of an inning.
Also "If two or more relief pitchers were similarly effective, the official scorer should give the presumption to the earlier pitcher as the winning pitcher." Gregerson and Neshek were very similarly effective. I suppose you could argue that Thatcher deserves the W, because he began the 8th inning (after the Astros re-took the lead) and retired the first batter, whereas Neshek did hit a batter while pitching 2/3 of an inning.
There is virtually no basis for giving it to Gregerson, unless you believe retiring the 2, 3, and 5-hitters in a 1-run game in the 8th inning don't qualify as "crucial outs".
