[nattybumppo]

I asked an astronomer friend of mine to look at the specs and got a small list of advantages:

-No atmosphere. Seeing would still be a considerable factor; getting 1 arcsecond resolution on Earth is not easy.

-No clouds

-Ability to focus on the same object for an extended exposure

-Infrared

-Can look north and south

There are a lot of advantages to this, even with their aperture size.

[lutorm]

Actually, not infrared but UV. They seem to have filters in the vacuum-UV which can't be observed from the ground. The near-IR out to 1.1um that they are going out to is not really a problem from the ground.