Yep, I think it´s worth the price - at least for Intel Mac users like me. Works rock solid on my Mac Pro. Furthermore you´ll get 720p50p support for the PAL HVX200 if you need to edit such material.
The upgrades are so cheap, I don't see why it wouldn't be worth it. I just upgraded but haven't really worked with it yet. Mine was a 4.2 or something so I had to pay the big bucks ($149) for the 5.7 upgrade. I've heard people say on the Avid forum that the improvements are great and it works very well.