A friend of mine at work just told me about the free WordPress App for both the iPhone and iPad. I’m composing this using the app from my iPad. Was very easy to set-up. Seems to run fine. One glitch I have noticed – the area that you type in to compose your post seems to have a sizing issue because text doesn’t wrap properly. You can be typing away and the cursor will go several characters past the right edge of the screen before the line wraps.
Update: I’ve quit using this app as I have found it to be really buggy. Hopefully all that will get sorted out in future updates.