Research overload is right! It sounds like you're pretty well informed on all fronts...
As per the MBUS, I'll just affirm you have made an excellent decision for your outdoor stroller-- it also handles very respectably at the mall and whatnot. Unfortunately, I haven't heard anything about airport transport, but it IS pretty bulky when folded down, so you'd be checking it in at the gate. Also there are some negative reports about how badly strollers get treated if you check them at the gate, so perhaps it's best to avoid that scenario if possible-- either by not taking it or putting it in a box (bit more work). I think it's a great outdoors walking stroller, but a bit of a pain to do air travel with.
I could recommend the Bugaboo as an everyday stroller, but it just isn't quite the same level of functional ease (folding and bulk) as more standard lightweight strollers and for the price, you should be able to fold it up and take it on the plane, but you can't, so if you're going for the MBUS already, you're looking at about the same amount of functionality from the Bugaboo (in general)... it's just not the compact piece of machinery that the classical umbrella design is.
The everyday stroller that might be the answer answer would be the Maclaren XT for overall functionality combined w/ a lightweight build, but if you must have the infant carrier compatability, the
Maclaren Global Buggy or the
Zooper Swing are your best bets (they weigh the same at 19 lbs although the 2004 Global Buggies are 17 lbs).
Although they're not much lighter than the MBUS, they are certainly more compact when folded down (mostly b/c of the differences in frame and wheel size). From my overly-researched perspective, the 19 lbs is only heavy to a very small percentage of owners, so I'm comfortable saying that I don't think you'll find either of these strollers too heavy for everyday use, although both strollers' folding processes have a learning curve.
The one main negative for the Maclaren Global Buggy is the same problem Maclaren has with all their strollers-- the canopy design is less than stellar and has to be treated w/ care when folding it down, otherwise the canopy frame is compromised and will start flopping about.
In terms of preferences between the Global Buggy and The Swing, I think you get more performance for your money with the Swing (and loads of accessories as well). So my advice, is to go for the Swing as your everyday stroller, but be prepared to use up a bit of patience learning how to fold it down.
Also, I think you're pretty close to having all the information you'll ever want and if you do purchase any of the strollers that you mentioned i think you'll be quite happy w/ them despite the fact that none of them are the perfect stroller. (I love the designs and consideration that went into both the MBUS and Swing and have heard more positive things about these two strollers from a wider range of parents than any other strollers on the market (even beating the Bugaboo for raves).
There is one other stroller in the lightweight sector which has loads of potential but I lack the consumer info for: the Quinny Zapp-- it is currently claiming to be the smallest fold on the market (fits in the overhead compartment for flying), and accomodates infant carriers. You can check out the website at:
Quinny-Zapp (and click on the UK link). Unfortunately, they don't have any distributors over here in the US, so I think it would only be possible if you have friends in England who might ship it over for you. Like I said, I don't have enough consumer info, but Quinny is a great stroller manufacturer coming out of the Netherlands, so it's probably pretty much what it claims to be.
Good Luck w/ your search! Let me know if you have any more questions.
Mara