We knew after a year on the road in our bus that one key upgrade before another long road trip for us would be a better way to deal with the unspeakable moments. Our last trip consisted of an old nalgene bottle, a gogirl and a folding toilet seat with some doggie bags. That system worked, but it was far from comfortable, so this time around (with a larger vehicle and ample storage space) we decided to go with a thetford porta potti, which is not only stable and comfortable but actually flushes.
We've only tested the system for a week, but so far it's been great and has increased our comfort dramatically.