I visited the US on the VWS last year about 6 times. I have a DUI conviction from the US from the early 90's (three glasses of wine, great). On each occasion at JFK I have been hauled up for 'secondary inspection', despite ticking all 'No's' on the green VWS form, their system flags me up each time. This has now happened about 20 times over the last 5 years or so. The starting point is missing I-94 exit cards from the mid-90's on their system, (nothing I do seems to clear these errors) then they start digging, and hone in on the DUI.
On almost every occasion they have asked me about this DUI. But, satisfied that I have committed no other crimes, I have always been let on my way. My impression is that as I have not lied, and I have not committed multiple crimes equating to Moral Turpitude (Google for the 'Foreign Affairs Manual'), I am eligible to enter. (That said 'secondary' is never a particularly pleasant experience).
It is only on my last visit, that on spending so long in the US of late, that they accused me of working there ilegally and told me I had to have a visa, which I now have.
p.s. So, I'd say, you sound as if you're fine on the VWS. But if you want more comfort on this read through the FAM as to what 'Moral Turpitude' is...
http://foia.state.gov/masterdocs/09fam/0940021 aN.pdf