Yes the climb up the PYG track is certainly a trial. The combined effects of the previous 5/6/7 hours effort, cramp, weather, and the crowds, have led to me losing my rag a couple of times, and finding it very hard to keep it together when yet another person walks into you whilst not looking.
The Peris climb (over Lliwedd), despite being significantly harder, is actually more pleasant due to the lack of crowds, and you only really have to deal with crowds on the final 100 yards to get up onto the very summit, and then the short section down the railway until you get to the Snowdon Ranger Path).
Although taking each climb as a separate entity, i find the climb up onto the Glyder to be the hardest on the Welsh 1000's....
Despite the drawbacks in the first paragraph, i still think it's the finest fell race out of all the ones I've done.
When you're coming down off the Carneddau and you look up and see where you're going next, it's frightening!