I PvPd a ton before the changes, and still PvP a lot but at a slightly decreased amount after.
I was hoping to see at least one story of someone who started PvPing in response to 5.3 changes. I'm sure they exist*, but I have a feeling that Blizzard overestimated the impact of selling world of warcraft accounts to their changes in encouraging newbies to PvP, at the cost of alienating people who worked hard for their PvP gear. To be fair, I also think the amount of people saying "I quit" to the changes was very overblown too. It was, and still is, very discouraging that they nerfed PvP gear so hard.
I can say for certain that the number of competitive games games has gone up since the change, which is great. It used to be that the outcome of a BG was determined 90% of the time before the gates even opened. Now it's maybe 40% of the time. The role-matching is great, but either it's buggy, or idiots are trying to game the system to "shorten their queues" (hint: it doesn't) by selecting off-roles, because I still get games where it's 3 healers to none.
I suuuuuuuck at Arenas. Suck suck suck. So I don't know how I would begin to earn enough CP quickly enough to compensate for my fast wow gold suckitude. We can only otherwise earn 200 a day through a RBG and the Call to Arms BG, right?
I think my trouble with the whole thing is that you have to put a lot of time in to get good, but you aren't getting rewarded very well during that time (really, at all, unless im missing something), and that's a pretty strong disincentive. Furthermore, what's the point of a CP catch up, if I can't seem to win enough to accrue it? To me, these things combine to say "don't bother."