It's just the typical "sorry about this, accept my part in demise of M, don't want a D, I'm willing to work with you on the issues, can't tolerate an open M, both need to make some decisions" letter we've seen here before. No blame, no judgment, just an offer to R.
Yes, I know -- save the 2x4's. . . .
Hey, no lumber from me, my twin brutha of a different mutha. In fact, I wrote one myself and gave me to my wife. I'll have to see if I can find a copy and post it here, minus the names and stuff. You might enjoy it. There is something to be said for getting one final, hit-all-the-right-notes statement off of your chest, and as long as you're authentic in what you state I really don't see anything wrong with it so long as you're not expecting it to be effective.