I don't know what the old ones were like but I have a 2008 Tarpon 160i and LOVE it.I am a 6'3" guy that weighs around 260lbs and the Wilderness Systems Tarpon 160 is a great,easy,enjoyable boat for me to paddle with my friends on easy rivers/calm lakes.
I went ahead and got a 2009 T-160 about a year ago. The seat, cockpit, and the hull have been redesigned. The orbix hatches are awesome. It's great. Not quite as fast in flatwater as the T-160i, but in choppy water it is a lot faster. And since we have a lot of wind and chop here, there isn't much that I would trade it for. The only negatives I have found in it is that the higher profile catches the wind a lot more than the older Tarpons and the seat isn't quite what I thought it would be but I just added a skwoosh pad and it is fine now. I have had this out under a variety of conditions, from calm to stormy, small bayous to large bays to surf and it is pretty much the ideal fishing kayak.
I have the 2008 T-160I and my buddy just got a 2009 T-160. And we noticed the same thing. Mine has the rubber press on hatches and he has newer hatches which are really nice. Mine sits lower in the water and is a little faster in calmer waters. There are pluses and minuses to each one, but over all its a great boat.