I can't really answer your question, but I just wanted to add that I actually bought a brand new 2005 Triumph that had been sitting in a Babies R Us store for years, obviously as a floor model and it was reduced BIG TIME. And to make it a final sale, they knocked off an additional $20. It was in perfect condition and looked brand new still (clean, not faded).
There was a 2008 right next to it, and my DD sat in it, and she said to me that the 2005 was more comfortable. It actually looked wider for some reason and not as tight (narrow) in the shoulders. The 2008 seemed a little more padded though and the straps are fancier (colour wise), but since DD is 6, that is not necessary and the 2005 serves our purposes just fine for our trip. I don't think there is much difference between an 07 and and 08, but of course there was a difference between the 05 and 08. I would save the money and just get the 07.