How I Met Your Mother was very hit-or-miss for me but I still watched it through til the end. For me, the ending was a huge disappointment -- it wasn't necessarily a surprise, but just the turn I was hoping they didn't take. I was young when Friends was popular, and my family didn't watch it while growing up, so I guess I'm happy I experienced HIMYM. The jokes are popular among my circle of friends and overall it did have some funny moments, so I don't regret watching it.
I agree with you. I didn't like the ending either. It wasn't like a huge surprise, but a felt a bit deceived. Overall, I loved the show though. Barney and Marshall are my favorite characters and they liven up what was otherwise a cheesy love story.