I have family up there and have visited the area as long as I can remember. My cousin currently has a home in Hammondsport and has a fabulous view straight up the lake toward Bluff Point. I enjoy looking at the fine lakefront homes, and the village of Hammondsport is postcard-pretty. Keuka is my favorite lake for boating- clear water, numerous waterside eateries. It's big enough to not feel crowded even on weekends. Most of the boat traffic is local folks because there's only a handful of motels and few marinas. Fortunately, it's not overrun by jetskiis. There is a 45 MPH speed limit on the lake.
It is deep (I think over 300') and the dropoff from shore is pretty steep. The water stays cold well into July, so bring wetsuits for skiing. There's a nice state park at the northwest tip with a swimming beach. As I recall, the only navigational markers are in the Penn Yan canal and around Branchport, where the water is shallow. The water clarity is stunning- I've often seen the bottom in 20+ feet and can watch the fish hit my bait. Speaking of fishing, bass and muskie are better on the smaller lakes (Waneta and Lamoka, just to the east) but Keuka does have lake trout.
Rob