Last night my friends and I took the four hour night tour with Daniel as our guide. The tour took us through Puerto Madero, San Telmo, Ricoletta and other towns along the way.
The tour definitely had the right balance of sight seeing v cultural experiences with casual stops for Choripan from a street vendor and a beer at Plaza Derrago whilst watching a free public Milonga (Sundays only).
The four hour duration flys by and the bike ride is not at all Taxing.
The price is too high at $50US however a quick search suggests there may be a little cartel type action going on in the BA bike tour industry with all charging the same.
Urban Biking use Bikes made from bamboo, a unique and interesting trait of this company and if you choose do the tour you'll soon notice everyone in the street looking at you (or more specifically the bike).
We got a small gift at the end, a nice touch on a good tour.