Climbing definitely does get easier with practice. It still hurts though because you just tend go up the hills faster but at least you have the option of slowing down rather than dismounting!
I'd still find a few hundred yards of 12% difficult. I can do mile after mile of 4% or 100 yards at 20% but fairly long, fairly steep hills really get to my back.
I've climbed Holme Moss from the Holmfirth side about 5 times now. 3 times I found it really hard and had to stop to stretch my back. On a couple of occasions when I was fit I really enjoyed it and didn't find it too bad. I've never done it into one of the strong winds that you can get up there - that would be simply horrid. Oh, and watch the descent towards Woodhead! It's not hard to get up to 50+ mph and getting caught by a gust of crosswind at those speeds is a bit scary...