I agree with Michael. I remember that Mayson didn't bother me at all while the series was running. There were times when I was frustrated with Lois that I actually entertained thoughts that Mayson wouldn't be bad for Clark. Yet when Dan came on the scene, I found him almost intolerable.
I suspect that the males on the board will be more ok with Clark having a past, and the females with Lois. It has to do with who you identify with, I guess.
I know that several of my stories have had Clark having a past...Single White Kryptonian being a big one. Duet had him as a single father. In Family Hour he had been married to a villanous Lana.
In each case those were past relationships which were long over, although the aftermath wasn't. The main focus of the story itself was on Lois and Clark's currently developing relationship.
I have to admit that the idea of Lois married to Lex and having sex with him regularly (or Dan for that matter) is disturbing.
I guess the question is, are past relationships ok as long as they are over by the time of the story?