Well, it's hardly the end of the show. It's likely to remain on air (or on cable) through the miracle of syndication for the rest of my life and probably longer. That said, I'm still a little sad to see Friends end. I remember watching the pilot all those years ago in my little basement efficiency and even if I missed some episodes (and probably a season or two) when they aired in primetime, I know I've seen every episode at least five times in reruns.
During the 10 Years of Friends (a.k.a., "The One With All the Others: A Friends Retrospective") clip job that preceded the finale, I found myself finishing more of the lines than not, which is kind of sad in a way, but it still made me laugh.
As far as series finales go, "The Last One, Part 1" and "The Last One, Part 2" (the only episodes besides "Pilot" that aren't titled "The One With [or Where] ...") didn't make the best end to a long-running series (probably M*A*S*H), but it was far from the worst (may well have been Seinfeld). Actually, M*A*S*H was an easy series to end because the end of the Korean War provided a natural way to end the series; Friends is similar in that the characters (excepting Joey) are all ending their carefree singleton lives to one degree or another (“Lifechanges ... Arrived,” perhaps?) but it's not the sort of clean break of an armistice.
There were some low moments. The Chandler-Monica adoption storyline got really uncomfortable for me at some points. When Erica (the birth mother) was first introduced, she wasn't as dim as she's been over the past few episodes, and the writers seemed to take more care with the complexities of adoption. There was Monica's thank you to Erica after the birth and naming one of the babies after her, but it hardly made up for how all the complexities of adoption were totally glossed over during the past few episodes. (True, it's a sitcom, and the earlier infertility episodes weren't the best at covering the complexities of that issue, but they tried a little harder, perhaps because of Courtney Cox's own experiences, than they seemed to with the adoption storyline.)
I think I'd also have liked Joey to at least get a phone call setting up his move to California. I guess this means the pilot for Joey will have to start with leaving New York (maybe with a cameo by a Friend or two?). That said, I don't have any great hopes for Joey; the teaser that ran during 10 Years of Friends looked on the lame side.