prathmann

1) loosen seat clamp (esp. easy if it's QR)
2) slightly lift bike while the seat post slides down into frame an inch or so
3) undo rear wheel QR and drop rear wheel out of dropouts/chain so you can pull it back and lift it up
4) lift U-lock and bar releasing the seat of the bike
5) make off with all of the bike except for the rear wheel (but the loops holding the U-lock to the bar look rather flimsy - so cut these if you also want to take the wheel/U-lock with you and cut the lock later at your convenience)

In areas with strong concerns about theft I'd be much more assured by the type of lockers used in our local transit stations. Each rectangular locker holds two bikes in triangular spaces. The locker doors have small holes so you can see if a locker is occupied but it's very hard to see details that would let you determine the value of the bike inside. They keep the bike both secure and sheltered and also let you secure some additional personal belongings as well as things attached to the bike (lights, cyclometer, bags, etc.). Credit card activated, they charge 3 cents/hour for parking.

Both this design and the lockers have issues with some non-traditional bike designs, but the lockers appear to be more accommodating than this rack design. The lockers mainly have issues with bikes that are too long to fit (tandems, some recumbents, some cargo bikes, etc.), or too tall (ordinaries, tall bikes, etc.)