Hi. I had an extensive thread at the end of last year on the Marco Sky stroller. I know Levity has one too.
So far, I am quite happy with it. It's not as good as a side by side 3 wheeler (I had a Steelcraft), but for what I use it for, it's okay. I use it to drop DS off to school, and in the shops. At the shops it's great because it is only as wide as a single stroller, so I can fit in all the ailses and also at the checkouts. It's also not that long (just under a meter when open) so it's not too heavy to push. However, it has virtually no basket to speak of, so there isn't really anywhere to put your shopping. I just hang a few coles green bags off the handles to put my shopping in. It is also quite expensive ($400-).
You can only recline the back seat, so if your girls are still sleeping in the pram it's probably not ideal. Mine are 2.5 years old, so we don't need this option.
The pram folds down like an umbrella stroller, but is quite long when folded (I think about 1.2m), so your boot needs to be wide or long enough, but overall, it takes up a lot less space in my boot than the side by side.
On the website, it says the prams capacity is 15kg in both seats. One of my girls is 14kg, the other 11kg, so we are close to capacity, but I still find it quite easy to steer.
Anyway, that's my experience with the Marco Sky. I'm happy with it, but it may not suit everybody. If you have any more questions, please ask.