I've done it several times with ED80 scopes. But... they're so consistently good that I don't really regret it as such: when I want one again I can usually find one for a good price with consistently good optics, so no great loss!
But... I sold an old gold-tube ED100 years ago, then on a whim re-purchased the black diamond version. Only sold that one to help fund an ED120.... I think.... (might be losing track)
Ironically, even though I own a Tak I actually regret the fact that I don't have an ED100 still (or again) as it's nice sometimes to have a "beater" scope that still performs well.