At the last Car Seat Shopping Debacle Update, I had just bought the Britax Roundabout online and was waiting for a CPS Tech to come check the installation of the Cosco Scenera we already had. Well, then the tech came, and she was really helpful and super nice, and I mentioned that I'd just ordered the Roundabout and she looks at me and says, "Is there any way you can trade that for a Marathon, instead?"
And she convinced me to try it. She actually had a Marathon in her car that her son uses, so she was able to pull it out and put it in the Fit to show us how it would workj space-wise (quite well, actually). Then she explained that although both the Roundabout and the Marathon can rear-face up to 35lb, but the fact that the harness slots of the Marathon are higher than the Roundabout (and that most kids outgrow their seats by height before weight) means that D could potentially sit rear-facing even longer in the Marathon. I'm not sure I'm crazy about the idea of D sitting backwards till he's potentially 4+ yrs old, but then again if it really is that much safer then it seems a small sacrifice to make, right?
My biggest reason for opting for the Roundabout was a concern for the size of the seat so being able to actually see it in the car and see that it would fit fine did it for me. Luckily Amazon hadn't shipped the Roundabout yet so I was able to call and cancel the order, and then we found Marathons for sale at Costco.com for $230 (which btw includes 2-day shipping) and now lil' D is riding in style in his Britax Marathon car seat.
If that whole story seemed totally confusing, it's because it is and I'm very impressed with anyone who's actually kept up with the whole saga.
Anyway, I'm pretty happy with the Marathon so far. It was ridiculously easy to install with LATCH, and I even got the rear-facing tether attached. I'm having slight issues getting the harness as tight as I'd like (and having to untwist the supposedly twist-free straps), but I'm pretty sure it's safe enough as it is. And D seems pretty comfortable and happy in it. =)