Is Instapaper worth it?

I'm currently a heavy user of Pocket, but I'm interested in Instapaper (mainly because of the Kindle support and the fact that everyone seems to use and recommend it). But is it worth it? Pocket is free and looks great, and I'm not sure if Kindle integration itself is worth £2.49. Do you use Instapaper? Why not Pocket? And is it worth the cost?