The more I play with Messenger, the more I think it's a pretty good card. And I'm just talking about the top part. +Buy and putting your deck into your discard pile together make for something that's often worth the terminal action slot, in a way that Chancellor and Woodcutter aren't. It's effectively two kinds of acceleration in one (three if you count the on-buy that also accelerates your opponents).
One benefit I've been seeing recently is that it protects you from bad reshuffles. I'm talking specifically about those engines that use some sifting to get through your whole deck, leaving a bunch of junk in the discard pile, which you then have to be careful not to shuffle back into your deck (if you can't draw it all). With Messenger, you can just draw as much as you can, potentially netting you a few extra $ if you discarded Coppers, or just getting you whatever ancillary effect your draw cards are giving you (like the Torturer attack). Chancellor did this too, but it was so weak that I never got to see it much.
Maybe I'm being a little bit Roadrunner here. Has anybody else been impressed with Messenger? If you haven't been buying it, I recommend you try it (ideally right after your opponent shuffles, and right before you do).