Can you use a dimmer with a can (recessed) light conversion kit?
I recently did the exact same thing you're evaluating. We used a conversion kit to install a pendant light above our sink where there was previously a recessed light. As far as dimmability goes, that's mostly up to the switch and the bulb you have, i.e. you have to have a dimmer switch and a compatible, dimmable bulb. We went with Leviton in this particular instance, though we have Lutron dimmer switches elsewhere.

One thing we've noticed, since we're dimming a single bulb, is that we have to find a "sweet spot" on the dimmer to prevent flickering in between brightness levels. It's a minor nuisance for the flexibility of adjusting the brightness.