I just got took a 4 hour flight last night where the person in the aisle took up part of my middle seat.

I would 100% pay for that seat. I personally don't mind not being able to recline. Being next to the lav can be annoying, especially if you are trying to sleep, but it's not the end of the world.

But anytime I get the chance to pick a seat, just pick something you will be comfortable in.

Also, a pro move:. If you are flying in a couple of months or weeks, check the same flight for this week to see what the load looks like. If today's flights had a bunch of open seats, it might be worth gambling on buying a window and an aisle in hopes that nobody buys the middle seat. Holidays kinda muddy this tactic (it's a holiday week in US).