I ride a DaHon folder to commute on some days; in the past it was 100% (for a year and a half), but one morning the DaHon greeted me with a blow-out (ka-boom!) on the back tire as i was rolling it down the driveway to start my commute.
Not wanting to take the time to deal with it right then, I grabbed my road bike (700C wheels compared to 16" on my DaHon Curve) and wow, what a difference in riding comfort and to some extent speed. Now, I do ride the Metro train for 11 miles in the middle of my commute, but since there are "bicycle cars" now, I haven't found the full-sized bike to be as much of a pain as I'd anticipated.
Sometimes it's bit more of a squeeze getting in or out of the train, but usually, no problem. So now I am on the fence; still like my DaHon, though with all the stop signs and traffic signals on my route, it is only about 1 mph slower than my road bike.
Plus, getting to the train platform means walking down lots of steps, which is easier with the road bike. Similarly, carrying the bike up the escolator on the other end of my Metro ride is easier with the road bike.
All that said, while I am still on the fence on this issue, I am leaning more to the road bike side. Time will tell.
Rick / OCRR