I like the idea from a simplicity standpoint -- with the right chainring, you can get an acceptable gear range from most non-racing cassettes/freewheels. (For instance, I wouldn't mind making a 1x5 out of an old 10-speed someday -- with a 42T chainring, a 14-28T freewheel, and 700x28 tires, that's 40-80 gear inches.)

I've heard that chain drop can be a problem, so you have to factor in what device(s) you'll use to keep that from happening.

As for the cranks... do you plan to replace the crankset, or just use the middle ring from the triple? If your chainline is good, then I'd honestly go with that. Otherwise, you may need to replace the bottom bracket (changing the spindle length) to space your chainring just right in the middle of the cassette.

- Scott