We bought the Chicco Cortina travel system 2 years ago, and I still think it's one of the smartest buys we made for the baby!
I love the ease of use for the infants seat, it's nicer features- the infant insert/head support, the ease of adjusting the height, easy to get the infant in and out AND get a snug fit, every time. But yes, it is heavy. Especially when you give birth to a 9.5 lb baby.
I also love the stroller. It's handles easy, the handles adjust for differently-heighted (if that's a word) parents, and it has held up 2 years of abuse of being put in and out of the car, countless trips to the park (that doesn't have sidewalks to get to the playground so you end up going through the grass), many, many walks on pavement, sidewalks and gravel, and it still works great (though it's starting to look like it's seen better days...but it's mostly cosmetic, nothing a good cleaning wouldn't cure!). It's also easy to fold, and the parent tray is great for your keys, phone, and beveridge of choice. The toddler snack tray has come in handy too, and it snaps out so you can wash it if it gets too gross. Also, the whole front bar comes off, so as the child gets older and wants to get in and out more, it's easier.
The only thing I would improve is the sun shade. It's okay, but compared to my friend's zooper waltz, it's skimpy.
As for the usefulness of a travel system, I really think it depends on the mother/family and lifestyle. I was on the fence on how much I would really use it as a travel system. It turns out my son didn't like to "travel" much while the infant seat was in the stroller. He preferred either to be carried (LOVED my moby wrap too!) or ride in the stroller. I live in a cold winter climate, and while I wasn't much of a mall person before I had my son, I found myself loving what the mall had to offer in winter- a great place to come in winter to get out of the house, go to target, B&N have lunch, only have to get my son out of the car once- and you stayed warm while doing it and even if you wear the baby (which I did most of the time), the stroller makes a nice place to put your coats, bags (especially when Christmas shopping), etc.
That said...my son outgrew his infant seat by Thanksgiving (like I said, big baby...was 23 lbs by Christmas @ 6.5 months). I know there's a Chicco infant seat that goes up to 32 lbs now. IF I could go back in time, that's the one I'd get now. Because, if you live somewhere where it gets cold in winter, it is really nice to be able to get bundled up inside, and only have to worry about putting the infant seat in it's place (even if it weighs a ton w/ your 20lb child in it).
Graco's snugride carseat (it too has a model up to 32 lbs), gets top safety reviews, so another option would be to get that infant seat and the cortina stroller...separately (because personally, I think the cortina is a great stroller at a decent price). I just reccomended that option to my brother-in-law and his wife...but she was concerned that the infant seat and stroller wouldn't match. If that's an issue for you too, I guess that wouldn't be an option.
Anyways, sorry this is such a novel! Hope my experiences help you somewhat!