I work for Shoreline, we run the Architecture tours up the river. Im usually doing water taxi stuff, but people come up to us every once and a while saying how much they enjoyed it. As a fellow STer I can hook you up with a discount or maybe even a freebie, PM me if you're interested.
Go to the taste, I've worked there the past 2 seasons (we run a taxi out of buckingham to the pier) and the stories of gangs and ridiculous crowds are way overblown. Its a bit pricey, but still worth it.