Another happy Britax owner here. I bought a Graco when my son needed a convertable seat, and boy was that a mistake. I always hated it, but never felt I could spend the big bucks on a Britax. 2 years later, when my daughter was ready for a convertable, I just couldn't go back to the Graco, so I made the leap to Britax....and am SOOOO happy I did! It is heaven compared to the Graco (for a lot of the reasons already mentioned).
We have a Marathon, since our girl is very tall...I knew she'd grow out of the Roundabout too fast. However, it's a large seat, and can be too big for some cars. Babies R Us will let you test out the carseat in your car to make sure it fits first. (you just have to leave your driver's license at customer service)
I got the Cowmooflage design online, since I didn't like the designs in the store either. Most online retailers sell it with free shipping and no sales tax. Britax doesn't allow coupon codes unless it's a closeout design, so you'll probably have to pay full retail. But, in my experience, it's WELL worth it!
Good Luck!