I don't own one yet, but have two on order for my wife and me. Bought the Brompton for use on multimodal travel. I know that there are other bikes suited to this purpose but I could not find what I thought would be a better choice. As an example, here's a brief preliminary itinerary for a 16 day trip planned for September.

Fly into Barcelona.
Transit to city center. Rides along Las Ramblas, the beach etc. tram to Tibidabo and ride down to city, assorted subway connections. Possible day trip north on bus to the Dali museum.
Ferry to Mallorca. Ride on the south part of the island and kick back on beaches.
Fly from Palma to Bilbao. Spend 1/2 day cruising Bilbao and bus to San Sebastian. Ride around for a couple of days and bus to Pamplona. Ride the route of the bull run and then head out on the Camino de Santiago. Spend a couple of days riding the camino and wine tasting in Rioja.
Arrive in Burgos and bus to Salamanca for a couple of nights.
Bus or train to Madrid. Use transit in town - parks, plaza, tapas etc.. Day trips via train or bus to Toledo and Segoiva.

We'll use t-bags as our only luggage but will have small packable backpacks as needed temporarily for picking up provisions. I m sure that other bikes could be used but the Brompton seemed the best choice to us, for a trip like this.

I have usually hung out in the tandem forum but spent quite a bit of time lurking here and you all are a helpful, informative and entertaining group. I hope to be able to start participating more.