Couple pointers on the upcharges:
You pay extra to pick your own seats; otherwise they can assign you randomly. We didn't care because the flights are so short, so we didn't pay the upcharge. Whaddya know, they "randomly" sat the three of us together on both flights. In other words, don't bother paying for seat selection.
Also, when they first started, they were charging $5 more per carry on bag than they were for checked bags. You still get a "personal item," i.e., purse or messenger bag, so imo it was a no-brainer to opt for the checked bag, which is up to 50 pounds, versus the much smaller carry-on limits. I gather many others figured the same, because they recently changed it to the same price for carry-on and checked bags, but imo the same logic still holds. We pay for one checked bag each way, and for short stays two or three of us can easily make do between sharing the the 50 pounds, and then each having one personal item.