Wanted to add that despite my frustrating track record with the cheap pregnancy tests, I think I've had better luck with the cheap OPKs. I say "I think" because one test this weekend came up positive for an LH surge, but I wasn't charting or anything (officially this is just a test month, not a TTC month!) and this is the first cycle I've tried OPKs, so I can't confirm that I indeed ovulated shortly thereafter. And I have no idea how often OPKs come up with false positives -- is it rare as in the case of the pregnancy tests?
In short, I'm not sure the OPKs from 2weekwait.com are necessarily flawed -- at least in my experience thus far, they seemed to work OK. The HPTs are the ones I'm starting to doubt.