The lake is pretty and the 25 minute boat ride around the lake was ok. Better lakes are found nearby so I would not recommend this over Bodensee (Constance) but ok for a drive through. We made the mistake of staying a couple of nights. Huge tourist trap.
The restaurants were horrible around the lake, shamefully so. Luckily, trip advisor was right in that the number 1 restaurant JOSTALSTUEBLE was a 15 minute drive and well worth it; excellent dinner. The next night we ate at a German-Italian restaurant right up from the lake and it was horrible. The Cordon Bleu was raw and the rest was a reheated frozen mess.
Shop after shop of horrible black forrest-themed junk, one after another lined the main avenue. I wondered who would by this junk and then all of sudden, several bus loads of foreign tourists unloaded in the parking lot. Titisee must be one of those "planned" stops on the way to the black forrest. I'm a very open and low key traveler, but avoid this place if you care for an authentic experience.