Bevvy – As a former MI customer, I think I can safely say what Brian's been polite enough not to say about their "competition": MI is absolutely no competition for OF. I actually do enjoy the structure of MI's workflow and I tend to like getting a stricter application of GTD principles (because I tend to procrastinate otherwise?). However, MI is not being developed by anybody remotely serious -they've been consistently horrendously late on their deliveries, and indeed according to the website back when I bought the software they should have been way into v. 2 by now... The new website, minus forums, emphasises the same types of promises that initially burned many enthusiastic users. Note that MI Touch is supposed to come out this month. As a cash-strapped student, I'd happily take a bet it's not going to be out any time soon.
Now, I'm all for supporting minor software companies with one or two people; unfortunately, in the case of MI, this has meant that this app has never seemed to be their priority, and that there have been consistently critical bugs in the app -by critical I mean that your data isn't safe there. As we all know the mantra of the trusted system, this isn't a good thing for a GTD app.
Again, I liked the design and workflow of MI, but it's anything but a solid app, and unfortunately the devs don't seem to care (I was one of a few users that had volunteered to moderate the forums when they existed etc., but we were never taken up on our offer).
Interestingly enough, if you like strict GTD implementation, I've found that one of my favourite "apps" (technically, a set of scripts) is Ready-Set-Do! It can look pretty weird at first and seem goofy, but it's actually got me through the end of my Ph.D. brilliantly. I'm moving away from it now as I'm shifting form having one humongous project to deal with, but as I'm returning to OF I find RSD still very useful in a number of ways: first, it provides an outstanding way to organise one's (electronic) desktop and generally all computer files [so ties in with OF where the latter leaves a gap for reference material management]. Secondly, it has a great implementation of reading organization, especially for electronic docs [but this can be achieved with OF too, I think]. Thirdly, it has a quirky voice-coaching. It can get annoying at times (although you don't have to go through it), but it can also provide a nice "push" when I get lazy.
Incidentally, RSD is a one-man product (he's a doctoral student, so that might help explain why RSD seems to fit an academic workflow so well), but the dev is *very* responsive. Then again, I don't think there's any threat to Omni's market there either ;-)