This is actually a response to some Ubuntu contributors very publicly leaving the project, and not to criticism from users. This is the blog post that started it off:

http://doctormo.org/2013/03/06/ubuntu-membership-2/

And here some the many responses in the past two days (remember, these are Ubuntu members, not random users), many of them agree that there's something wrong with the Ubuntu community of contributors:

http://randall.executiv.es/ubuntu-stage-next

http://blog.pault.ag/post/44821301540/ubuntu-the-community

http://www.jonobacon.org/2013/03/08/thoughts-on-recent-commu...

http://www.markshuttleworth.com/archives/1235

http://apachelog.wordpress.com/2013/03/07/divisive-leadershi...

http://www.markshuttleworth.com/archives/1232

http://smartboyhw.tk/wordpress_smartboyhw/?p=28

http://linuxgrandma.blogspot.co.uk/2013/03/thoughts-and-worr...

http://philipballew.wordpress.com/2013/03/07/confessions-of-...

http://princessleia.com/journal/?p=7670

http://ftbeowulf.wordpress.com/2013/03/06/freedom-and-commun...