I can chime in with my opinion, but of course, that's all it is! I weigh in around 160 lbs, so a heavier rider may feel differently.
I think the OEM suspension is fine for the street and low-speed offroading. I've definitely bottomed out when I was pushing the envelope in the rough stuff though. I could see upgrading the suspension when the original stuff is worn out, but I'm not in a hurry. You can't turn a TW into a MX bike, period, so for now OEM is good enough for me.
200-300 miles on a stock TW seat with a Coleman pad is no big deal for me, right around 300 miles I start getting sore. The type of riding I like to do on the TW involves a fair amount of stopping for little breaks and photo-ops, which certainly helps reduce the monkey-butt.
The great thing about the TW is how easily (and generally cheaply) you can get it set up to do just what you want to do with it. Trail monster, mini-ADV bike, street tracker, whatever. I understand that some weirdos even like theirs just fine left mostly stock.