Coming up on a year that I've been running a magic gear on my snow/rain/quick run to the dep bike, a Kona Smoke - 44x18 is a perfect fit. The chain tension does slacken a bit once the chain starts wearing, but I'm running a ring with an extremely tight spot on a cheapo sugino biopace ring, and it's still not enough to cause enough slack to raise the alarm, though it sure is bad for drivetrain wear.
When I first set it up I was running a really worn chain from another bike in the snowiest/saltiest month ($/chain conservation since it was going to be trashed that month either way), and shortly after that I started throwing chains. Put on a new one, no problem.
If you have "semi-horizontal" vertical drops (shallow ones that aren't exactly perpendicular to the chainstay, as is pretty common) you even have a couple of mms of adjustment, even better. I start off near the front of my "semi-horizontal" drops with a new chain, and by the time the chain's about done, the axle sits right in the drop.
I say ignore the naysayers and run it - you'll only wear stuff out faster and have tension problems if your chain is too tight (like mine is). Chain tension is the most overrated factor on a fixed bike imo, and it seems a lot people here must run their chains way too tight. It has to be tight enough to not get thrown, that's it.