My brother and SIL have this seat (Urbini Petal) with the Omni stroller. There little boy was born a couple weeks ago weighing 6.8lbs but left the hospital at 6 pounds. This seat holds him very nicely and it has a lot of great features for a $99 seat. The only downfalls I have seen so far are in the harness adjuster, when your are tightening it it kind of sticks towards the end, I think this is from the Velcro holding the excess slack together, hopefully this won't be a problem as he grows and is out of the newborn setting.
The other issue I have is with the base. The locking mechanism is on the base itself and if the green button things (sorry I don't know the proper term for these "buttons") are pushed down the seat will not lock onto the base. There is a large sticker with this warning right there in your face and it only takes a second to resolve the problem. I do worry about it though, I'm more experienced with car seats than my brother and SIL, and even I had issues securing it to the base (half of the time) when I helped them install it. You really need to be sure you are setting it on the base just right for it to lock completely, and always pull up afterwards to make sure it is secure.
Other than that, it's a great seat.
Amy