I disagree with Darren's first 3 recommendations!
While the Evenflo Vanguard & Victory and the Cosco Alpha Omega (AO) have fairly tall seatbacks, they also have relatively *low* top harness slots. This means they're great for extended rear facing (
www.cpsafety.com/articles...dedrf.aspx ) with a taller toddler, but they will be outgrown *much* earlier than some other seats when turned front facing (a front facing seat is outgrown when the child's shoulders are above the top harness slots). I've read quite a few complaints lately by people whose 2.5 year olds are too tall to use the AO harness, but don't weigh 40 lb and are definitely not mature enough to sit in a booster yet. I've also tried my 2.5 year old daughter in the Evenflo seat, and she is too tall to use that seat's 5-point harness front facing as well!
As Darren said, the tallest convertible out there (both by seatback height and by top harness height) is the Britax Marathon. It runs $239, but it also has some features and longevity that no other seat has. However, you don't have to spend $200 to get a nice seat that fits your child. <img src=http://www.ezboard.com/images/emoticons/wink.gif ALT="
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1) Britax Roundabout. (
www.britaxusa.com/ ) This seat has EPS foam (like you find in bike helmets) to help protect the head. It has built in locking clips, which make installation much easier in many vehicles. It has an *easy to use* tether which can be used both front and rear facing. It has straps which do not twist or wrinkle and a harness adjuster which is so easy to use that my 4 year old can buckle himself in and get his own harness *tighter* than the recommendation! (There are seats which take my full strength to tighten just barely tight enough. The recommendation is that you should only be able to fit one finger between the child and the straps at his collar bone.) Any harness slot may be used front facing (most convertible seats only have the top slots reinforced for front facing use.) It is very well padded. They are also usually expensive—approximately $200 for the Roundabout; however, Babylove.com has the non-LATCH version on clearance for $159.99, and some Right Start stores have the deal.
2) Evenflo Triumph. (
www.evenflo.com/ep/on_go/...h.phtml?nf ) This seat has EPS foam. It also has a unique harness adjustment system that uses knobs and a "memory harness". I’ve heard that the system can take a bit of getting used to, but once you do, it’s great! That avoids the problem many seats have with adjustability. The Comfort Touch version is well padded, but it also costs a little more.
3) Graco ComfortSport (
www.gracobaby.com/Section...TypeID=432 ) The straps on this seat are less twisty than many, though not nearly as nice as those on the Britax seats. The harness adjuster is also easier to use than some, but again, not nearly as easy Britax’s.
4) Cosco Touriva. (
www.djgusa.com/coscocat/c...uriva.html ) This seat is much more difficult to use and has a lot less padding than any of the seats listed above. It also has a very difficult to install and adjust tether. However, it is significantly less expensive, and if you are diligent about making sure the straps don’t get twisted and in ensuring that the harness is tight enough each and every trip, it is not an "unsafe" seat.
The seats I listed above all have a rear facing weight limit of at least 30 lb (remember, toddlers *must* stay rear facing until they weigh at *least* 20 lb and are a minimum of 1 year old, and longer is safer). They are compatible with a wide variety of vehicles, though you should always make sure a seat fits in *your* vehicle before making a final decision. They all have reasonable harness slot heights (lowish bottom slots and tallish top slots). They all have a 5 point harness, which generally provides better protection in a crash than an overhead shield does (see
www.cpsafety.com/articles...hield.aspx for more).
There are perfectly fine seats that did not make my list. Some have compatibility issues with many vehicles (but might fit your vehicle perfectly). Some have exceptionally low harness slots and might be outgrown much sooner than another similarly priced seat. Some are more difficult to use without being any less expensive. However, if you can say, "Yes," to each of the following questions, the seat may be the right one for *you*.
1-Does it fit your child?
2-Does it fit your vehicle?
3-Does it fit your budget?
4-Will you use it properly each and every time you go somewhere?