Just rode back from Gibralter last week in 2 days.
It's calms the nerves when you have 350 miles to do and the satnav indicates that you have no spare time for fuel/coffee breaks. I arrived with 3 minutes to spare.
Over the 2 weeks I was away, the extra weight of the fuel was only a problem getting the bike off the centre stand (with the panniers fully loaded as well). The rest of the time it was never a problem.
With the standard adventure seat, I only really needed to get off and stretch my legs when I refuelled anyway. Fuel stops tended to take 15-20 minutes, depending on queue for the pump/coffee/toilet etc.
One other downside was when a leak developed from one of the fuel pipe connectors up under the tank. Trying to lift the 41L tank off with 30+ litres of fuel in it was a no-no. Spent a few hours rounding up 7 empty water bottles of various sizes to drain the tank into.
Sitting on the bike all day isn't for everyone, but for me, having the fuel capacity to keep going was very reassuring. Also, as has been said before, you don't have to fill the tank to the brim.
Hope this helps.