I just sent this feedback, I thought maybe people might be interested in discussing it too:
This is going to be vague, but I hope it will be useful because I think this barrier for adoption of OmniFocus for me, will also apply to many other users.
I've been trying to use OmniFocus as part of my general workflow since I received an invite months ago, and I just can't.
I've thought hard about why this is, since rationally OmniFocus is almost everything I always wanted in a GTD app.
Despite having the option of using OmniFocus, when I need to make sure I do something, I find myself either setting an appointment at a vaguely suitable time in Google Calendar (my calendaring solution of choice, which will email, SMS, and/or pop up a notification), or sending myself an email and refusing to read it until I've completed the task.
I think the basic issue is that I don't trust myself to poll OmniFocus frequently enough to ensure that I complete a given task. Sure, once OmniFocus is already part of my daily routine, this isn't an issue, but its a serious inhibitor to the initial trust required to make OmniFocus a part of my daily routine.
I therefore tend to fall back on far from perfect mechanisms that either prod me (Google Cal), or which I do poll on a very regular basis (email).
I would urge you to think about how to make OmniFocus better at nagging the user to perform outstanding tasks, even if OmniFocus isn't necessarily running, or if the user keeps it minimized. Until I can put a task into OmniFocus, and *know* that I will be pestered in a reasonably effective way until I have completed the task, its never going to become my primary repository for outstanding tasks.
I know OmniFocus has some kind of review process for tasks, but frankly I don't understand it, and if I don't, many other users probably don't either - since I'm no idiot.
I hope you take this feedback in the sense I intend it, I would love for OmniFocus to be a part of my daily routine, I just can't see this happening until I can trust it to pester me to "get things done". This may be achievable with scripting, or with configuration, but something so fundamental should be easier to achieve than that.