I think the standard U, or STAPLE has a utilitarian charm.
Racks can be ganged at 24" centers, allowing two bikes per U. The most important design criteria for U-racks is leaving clear access space on both ends. Frequently designers put a row of racks up against a wall or other obstruction, reducing their capacity by 50%.
This type storage is for residents and/or workers in a building. Although it can be accomplished with U-racks, a secure bike room is a much better option. Thieves steal bikes, and parts from bikes, even in locked garages.
As bicycle use increases in urban areas, there needs to be bike parking located in the public realm. BIKE CORRALS are starting to be a common feature in bike friendly cities. Amsterdam has a multi-level bicycle parking garage located by the main train station.