I'm building a parallel setup for our VW LT mainly because I happened to score two new garrett 1544's from ebay very cheaply. The main reason however is to do something different than everyone (which usually indicates that it's stupid).
At least it's easy to weld exhaust manifolds as they are only 3-1, not 6-1 as with single turbo. I suppose they also will look cool, if someone wants to open the engine booth under front seat
Parallel setups are said to have better low-end spooling because of smaller components, but I think that can also be achieved easily with VNT turbos.
I'm going to use GT1544's own wastegates (normally open in 0.6bar), maybe modify them a bit to open in lower pressures, and add a simple boostcontroller to control them. This way I can get identical pressure to/from each turbo.
As our LT is used only to carry cars ("Pritschenwagen"), we're not going to try to make as much power as possible. It is registered in special car class allowing it to drive 100km/h (usually vans without airbags are only allowed to drive 80km/h), so we're going to use only as much boost that it goes easily this 100 km/h with 1400kg car "onboard" - supposedly somewhere between 0.4-0.8bar.