Catchpoint is clearly the leader in the industry on pretty much every metric you look at (aside from market share...for now), and blows Keynote/Gomez out of the water when it comes to features and support. Mehdi (the CEO) is accessible at all hours of the day and night for any and all questions, and his average response time must be under an hour. Catchpoint has everything you could want in a synthetic tool, and many things that you didn't know you wanted but you are ecstatic to have. I can't say enough good things about the people that work at Catchpoint and their commitment to building the best product in their space.
Room for Improvement:
The only thing that occasionally bugs me about Catchpoint is some aspects of the UI. It's not an easy problem, and I don't know how I would solve it, but because of the large volume of data that they are presenting and the various ways to slice it, you can end up with a proliferation of windows when debugging an issue. This is something that I expect to improve in the near future, since Catchpoint has rapid releases and is extremely receptive to customer feedback.