Friends was one of those shows like ER, where the cast was made up of relative no names (at least at the time), but unlike ER the main cast stayed together for the entire run. I think that allowed the show to keep the same feel and tone throughout the series. The writing was very very good in that they allowed the characters to evolve and grow over the course of 10 years but never lost the core of who they were over that time. They also did a great job of referring to old jokes without (for the most part) making them stale. For the ones that did, it got to the point that they would even poke fun at it (for example "We were on a break"). I also liked how the show relied on more than just sex jokes for the comedy (unlike many of the sitcoms of today). While there were certainly sex jokes throughout the series, the show did not lean on them and there were a lot of smarter jokes in the series too, that presumed the audience was smart enough to be entertained by other material.
The Blu-Ray set is a 21-disc set. The 234 episodes and some of the bonus content are spread across discs 1-20, and disc 21 has additional bonus content. The A/V quality of the set is good, but not outstanding, especially if you are a big A/V wonk. Even though the A/V quality is not perfect, it is a step up from the A/V quality of the DVDs. One big drawback (for some) in this release is that the episodes were only the ones that were broadcast. Apparently, the DVD sets included a lot of extended episodes, but this is just going to give you the show as it was intended to originally be seen. If that is a deal breaker for you, then don't waste the money. The extras include commentary tracks on select episodes, trailers, "Friends of Friends" featurettes, which give a breakdown of all the guest stars for that particular season, featurettes on the fans, the on-location episodes, gag reels, and more. The final disc also includes appearances by the cast on The Tonight Show and the Ellen DeGeneres Show, the "I'll Be There for You" music video, a couple of series retrospectives, and the original version of the episode "The One Where Rachel Tells Ross" which aired shortly after 9/11 and was edited because of a bomb joke.