Folding bikes rock.
I have a Bike Friday New World Tourist. I don't actually fold it that often though. I bought it more for the fact that it's an excellent touring bike that can be packed into a suitcase for bus/train/air travel. Still great for commuting, hauling cargo trailers, etc. too.
I have brought it onto GO buses and trains a whole bunch of times now, as well as OC Transpo and TTC buses and streetcars a few times.
If I were to get another folding bike specifically for the purpose of multi-modal travel, I would probably opt for a Bike Friday Tikit or a Brompton.
Cheers,
Vic