One thing to watch out for with the mobile lounges is that they can be delayed due to aircraft sitting on the tarmac outside the mobile lounge access ports.

I was recently in IAD, spent too long at Vino Volo, and had to hustle butt over to the A terminal. Ran into this situation. Several pax were getting stressed out about the lack of any mobile lounge movement. Finally did catch the craft, and made it to A1 (as far away as it gets!). What a &**( zoo that gate is, BTW. Boarded OK (although as last F cabin passenger, I had to find overhead space back in coach for my bags).

Moral of the story: don't rely on the ML's running on-time...