It doesn't happen all the time, but it does often enough to be a hindrance. I also find that the iPad versions of MS Office apps, while vastly improved over the last few years, still leave a lot to be desired. Excel for iPad is useful only for the most rudimentary spreadsheets. PowerPoint for iPad is quite good for viewing and taking notes in presentations but I wouldn't attempt to edit one with it. And while I don't spend much time in Word, whether on my work (Windows) laptop or on the iPad, the iPad version strikes me as very limited as far as formatting, tracking changes and other relatively simple functions go.
I do agree that true external monitor support for the iPad should improve the experience significantly. Unfortunately, most of the personal productivity work I would do with either an iPad or a MBA is in the evenings, in my living room, two floors below my office and desk. So, to me personally, the external monitor support would probably be of somewhat limited utility.
