Here's my take from experience. My grandfather owned the last living son of Poco Dell (a son of Poco Bueno) so I've handled and rode a lot of PB bred horses. He also owned a son of Poco Pine (another son of Poco Bueno) and I've still got horses that are sons and daughters of both of them. Rode both of them as a kid. The Poco Dell stud was super smooth but never got the chance to ride him out of the arena, I was really young. The Poco Pine stud was a blast to ride, grandpa bought us kids some goats to practice 'cutting' on him.
They are very responsive and somewhat sensitive but it's a good quality in my book and for a performance horse it's a necessity. They do well with a clear, firm but fair leader but don't do well with being domineered, very willing when you show & tell what you want but can say no in a big way to aggressive force. Can't say we've ever had a chronic bucker, plenty that did the first time pushed into a lope but that is pretty norm and they can do it big if they want to. One that bucked like a top notch rodeo bronc but only when in heat. Can't remember any truly nasty ones. Then there's my old man that I just lost who if not rode consistently he would give you a pathetic version of a bucking fit - really pathetic, like 2 strides of pathetically smooth bucking and then settle into a nice working lope. Going to miss that :( Now scoot out from under you, oh yeah. Athletic and quick, on the rare occasion they spook they are doozies and you better have a darn good seat. Stubborn, yep until they know who's in charge. If you're smarter than your horse, they're great!
Smart enough to do a bit of everything with. My grandpa was a huge supporter of the "all-arounder". My reining mare was also my jumper and speed horse, wouldn't recommend that, the sliders with screw in cleats are a pita.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.