I have chartered in both Champlain and the Chesapeake. Winds of Ireland is the only bareboat outfit I know of on Champlain and they were good. Boats not brand new but in good shape. Champlain is is a fun lake to sail on but in early Sept. it is hit or miss for wind (like anywhere else in the NE). very nice anchorages and some good boat-only parks with moorings. bring bug spray though.
chesapeake is great - it goes on forever, at least compared to a 5 night charter. a million anchorages, well marked but probably 18 million other boats out that weekend. i used Haven Charters in Rock Hall. I highly recommend them.
Maine would be great! have to pay more attention though. Big tides, rocks etc.