There's no FLGS near me running Encounters anymore, but when there was, the quality of the adventures was generally very poor.
Even a good adventure designed for the Encounters format wouldn't be worth paying for, IMHO, especially as there's no way to look at it and evaluate its value first. But all of that is based on the first couple of seasons' worth; I hear that it has gotten better since.
I thought the whole point of D&D Encounters was to attract new players. It seems to me that asking dms to pay for the advertising they're doing for WotC for free is going to alienate some of them. I realize that the Encounters material costs money to produce, but I have misgivings about the future of the program if they're going to start asking the dms volunteering their time to pay to play. (Why not just run something homebrewed instead, if your itch to run the game is so strong and Encounters is your only option?)