What could be better? Certainly not as narrow as a standard booster, the SecureKid DLX All-in-One is pretty wide at 27.7 by 19.7 by 19.5 inches, meaning if you are trying to fit three kids across a standard car's rear seat, you're going to have a tough time doing so. Also, while the extended headrest gives kids added protection during a side impact collision, it also reduces a child's ability to see his surroundings. On several occasions, my son complained that he couldn't see out the window — or for that matter, his brother in the next seat over — and he could only look forward. And, while most convertible car seats have a "base" on them that lifts kids up, this seat functions more like a booster on the bottom, so the seat is flush with the car's seat, so if you have a smaller child in the seat, it is actually difficult to see him in your rear-view mirror.
Finally, I found the chest clip on the five-point harness really difficult to undo — which is great in preventing kids from undoing it themselves, but really annoying to a parent who is trying to get her kid out of the car in a hurry. While I thought it was just me, several people tried it for me and had similar issues undoing it.