I'd bet that I'm a lot more cautious buying apps from the Mac App Store than I am from Google's Play Store, simply because Google's got that safety net of "Eh, this app isn't as good as it looked in the screenshots. I'll just return it." Trial periods also usually go a long way in convincing me to spend money on an app, especially things more costly than a dollar or two. A few months ago, I found myself debating between Totalfinder and Pathfinder- luckily, they both had a few weeks of free trials and I was able to determine that while pathfinder looked like it had more features, Totalfinder just felt a lot more seamless in day-to-day use. If I hadn't had the ability to sit down and get a feel for the apps, I'd probably have just said "fuck it, I don't need tabs and split panes that much anyways."

We're gauging the demand for a trial version at the moment and may decide to offer one if we find that many users are surprised by things not working as expected after purchasing the app (e.g. certain accounts not working, things that were unclear in the marketing, etc.)

To add a data point, I'm not going to give a chat app (a small utility, but an important one that I'd be willing to pay for) a second thought at $10 without a trial.

I'm perfectly happy with Adium right now. If you want my $10, there better be a trial to convince me to switch.

Echoing a third time - for any consideration on my machine, I'm going to need to take it for a test drive. $10 is non-trivial, and Adium is still more functional and already on my machine (oh, and free). I really do want to take your app for a drive, though. Please, please release a trial. Make it as short as three days - I'll use it enough to know if it's worth the money by then.