The soft keyboard does indeed go away when you attach a bluetooth keyboard. 🙂 In fact, if you get one with iPad/iPhone (usually marketed as 'iPad') specific hotkeys, there's one that you can push which will make the keyboard pop up and down.
As soon as you start typing with the bluetooth keyboard, it generally goes away -- though, some apps, like the Proboards app, aren't quite programmed right for the external keyboard.
If I understand correctly, the dock keyboard is basically a bluetooth keyboard with a dock attached, so it works just fine with the iPhone/iPod. 🙂 I remember reading that the 3G and 3Gs iphone models will fit into the dock, but the iPhone 4 won't. So, before investing in a dock, I'd definitely recommend making sure it'll work with your iPod.
I've used two different bluetooth keyboards with my phone -- a Rocketfish one, and a generic apple knock-off one -- and they've both worked excellently. In fact, I bought the knock-off specifically to use with my phone, since my Rocketfish is a bit bulky. The bluetooth pairing process is very easy and intuitive (as you'd expect from Apple! xD ). I'm very pleased. ^^
As for Google docs specifically, I have actually had a bit of an issue. While I was typing, whenever the document saved, the cursor would skip back to the beginning of the paragraph for a fraction of a second, before going back to the end. Unfortunately, I type fast enough that this could be three or four characters, which would end up in the wrong spot. X) Since then, I've been using the notes app to compose whatever it is I'm composing, then copy/pasting it to Google docs. Though, it was probably just an odd/isolated bug, and I've been meaning to try it again.
