for a backup carseat I think it would be just fine. The padding is minimal and if I were carting my little one daily I would upgrade to something a little more beefy just because I think it would be more comfortable for them. As far as safety goes I don't see the problem. Even the cheapest car seats still have to meet minimum safety requirements.
It can be forward facing and rear facing. It comes with a detachable head support cushion for infants. I started using this when my son turned one and it's been great! I really like that it can recline when forward facing; I have an adjustable back seat which makes a difference as to how far it will tilt.
On a side note, this car seat is very easy to wash and take apart. Something I learned during flu season!
I would not suggest this seat for newborns, although it can be reclined some, I think it would be best to use a carrier seat for the first few months. Beyond that, though, this seat is perfect for the following sizes and i expect to be using the seat for another couple years. (you kind of just know when they're big enough and can support themselves properly, no real set month for this).
Yes, I believe any infant over 5 lbs would be fine in it. It can be rear or front facing and does recline. We bought it when my grandson was 9 months old because he had grown out of the infant car seat we had. Had I known we could find one that would take us up to 35 lbs (I think it is) we would have purchased this first.