I think responsive layouts for a phone screen is fine, and generally better for browsing, although it would be nice to have a button to disable it.
However responsive designs for tablets are pointless. My iPad provides a great experience for browsing full size websites. But even more, I use my browser on my screen with a width of 1078px wide. I use Divvy to manage my window locations and sizes, and on my 1440px wide screen this gives me a space on the left for Twitter or whatever other social network client I want.
Unfortunately, in the last few months I've noticed a few sites that I use regularly now have far too much padding at the sides and show less content, all because it's supposedly a tablet. The recent rise in this is mostly due to Bootstrap, which is convinced my browser is a tablet. In the past I have found the width to be perfect for displaying almost every site I encountered.