There are several misconceptions in your reply:
We haven't even tried to build a permanent structure on another celestial body yet
You could argue the rovers were permanent, albeit their battery power isn't. They were still designed to last longer than a brief visit. Plenty of pieces of equipment were left on the moon with a more permanent function as well, just take a look at the reflector left by apollo 11 ( http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html )
a crappy space station in low orbit that keeps falling into the atmosphere and needs to be boosted periodically
This is absurd. The earth has an atmosphere that extends well beyond just the 50km you think of. A large station the size of the ISS creates plenty of friction with the remainder of the atmosphere and thus "slows down" in its orbital speed, causing it to slowly fall. This is a natural physical phenomenon that has nothing to do with the inability to design spacecraft, but is just a net effect of choosing an orbit at the altitude that it's currently at.
We shouldn't even be thinking about colonization of another planet until we've figured out how to build a permanent space station with artificial gravity,
Why? If we could successfully colonize the Moon/Mars, then why would we need artificial gravity stations? Artificial gravity sure is nice to have, but I'd rather have an atmosphere to shield me against radiation, and it's kinda nice to take a drive out to the Martian cliffs or even to just hit a golf ball in the moon sands.
and there's no atmosphere to cause problems
arguably, it's preferable to have an atmosphere, as it will reduce the engineering requirements for preventing leaks, IOW the structure will be safer if there is some atmosphere, even if it's not breathable.
atmospheres also reduce temperature fluctuations from day/night events, causing the temperature changes to be less drastic, again a win.
it would be fairly simple to build enclosed, pressurized greenhouses on the Moon to grow things
Plants might not grow that well being directly exposed to radiation for longer periods. They're also not growing as much in the 2 weeks that they are in the darkness, so it would be a lot easier to just use artificial light.
we'd just need to figure out how to make the soil suitable
The stuff the moon is covered with, "Moon dust" if you must, isn't "soil" at all. It's just ground up non-organic minerals. The word "soil" means that organisms have changed it in a geophysical sense, which hasn't happened on the moon. As such, the "moon dust" is highly unusable other than filler, and it will take massive quantities of organic matter to actually make stuff grow in it. You can't just plant a tree in the middle of the Sahara sands, water it and expect it to grow (it will just stay the same size, not grow fruit etc., and eventually just die due to depletion). The missing nutritional elements in moon dust will be a killer, and the fine grain will likely cause all sorts of watering issues.