Look for a 5 point harness and a front harness adjuster (Graco Snugrides are very nice seats, but only some of them have these features...just FYI...).
I am due in February and have a couple seats already... I have a Companion that I absolutely cannot stand.. perhaps it's a lemon, but that thing does not come in and out of the base easily at all, and it's extremely bulky and hard to get the handle down (and it MUST be down when driving). I don't think any other Companion owners hate their seat as much as I do, so mine MUST be a lemon (it installs beautifully, and I LOVE the anti-rebound bar, too, though!). I have a Combi Connection that is light and fairly easy to use (there are a few niggling details with the infant insert and adding a little foam bit to the seat that is required for head protection)...but it's light and you can leave the handle up when driving (have to leave it up, in fact). It is very easy to install without a base, so you can probably save money and not buy a second base if you don't use it in other cars very often.
I have a Chicco Key Fit, which is nice...installs better with the seatbelt in a Sienna than the LATCH, or so I've heard, but that seatbelt install is *awesomely easy* so it's not a big deal. The seat is heavy, but the infant padding is terrific, and the handle is optional to leave up. Overall it's very well engineered, and I couldn't beat the price at one step ahead of $107, even though it's a very drab pattern.
The Graco Snugride is a very nice seat, should install very well, not to heavy to haul around, fits well in lots of strollers, has lots of great cover options...no EPS foam for head protection like the three seats I have, but I've installed hundreds and they are nice and safe and very easy to work with.
The Safeseat is quite nice, but really very large... it's not the last rearfacing seat you'll want (you'll want a nice convertible to rearface taller than 32 inches, because rearfacing to age 2-3 really IS much safer than the bare minimum of 20 pounds and a year), so maybe you don't need such a bulky seat that will be hard to carry when you have a tiny infant. Think about your lifestyle... if you are doing daycare or multiple cars, you might want the convenience of an infant seat as long as possible, but if you are home and mostly use one car, you probably won't want to use an infant seat much longer than 6-8 months, when babies can usually sit up and you don't need an infant seat for going out to eat or whatever, and it's ultra heavy to carry, anyway.
Good luck choosing, there sure are a lot of choices nowadays (I personally don't like the base of the Peg Perego seats, but it should install fine in your van, and the new SIP model is spendy at 229, but also probably quite nice, if you like that one)