I just tried all four services at once and had a pretty similar experience. Kayak, Tripcase, Tripit, WorldMate.
Kayak nailed it with my house rental reservation which was an unstructured e-mail and pdf. I agree it was almost like a human did it.
Now Tripcase surprised me because at first it didn't register my house rental but about half an hour later I got an e-mail which did. It wasn't as well done as Kayak, it wasn't merged with my trip and not all the forms were filled out but I do give them honorable mention because it seems like they are implementing the same kind of system.
Worldmate gets a point because it automatically merged my flight/car/rental into one trip. The others broke it into two or three separate trips even though they knew where my home city was and that my flight there was obviously my flight home, not a new trip. However, merging is easy to do manually so isn't as big a deal.
Tripit just sucked, it didn't get any of the above. I hooked it up to my gmail to scan and it didn't find any of my confirmation e-mails (i'm not sure if it only works for e-mails coming in after the fact, but it does not make this clear so it is still a fail in the user experience). On top of that it costs the most and you have to pay for something as basic as flight alerts which is ridiculous in this day and age with a million free flight alert apps or from the airline itself and visually it looks the worst. I see no reason to use it.