For a few years my commuter was a brakeless bmx bike, and that was a TON of fun. 2.25" tires on 20" wheels that were faster than plenty skinnier, larger diameter, lighter wheels of the cyclists I'd pass.

It was nimble too; i could lay the bike near sideways and touch a pedal or bar end to the road before the real wheel would wash out. I could hop ~2' high (which is ~ half of what most pros can hop now, yeesh) plenty to avoid hazards or get up on the curb / median. It was durable. Very little required upkeep. ...actually I kind of miss it now.

The best commuter is the one you use to commute. I'm back to having one bike and am not in a financial position right now to change that. For some people, one bike is a blessing, whatever bike. Upgrading is out of the question, let alone acquiring a stable of steeds...