Get a system that meets Adobe Forums: System requirements for CS5
A MBP is below minimum requirements and - as you noticed - too slow for editing AVCHD material. You may be able to sell it and get a Sager instead.
There are many things on that MBP that makes the AVCHD performance extremely sluggish:
1) Only one hard drive. Adobe requires a minimum of two hard drives - one for the OS and programs, one for the media. More drives are better, but the MBP has an extremely limited number of even external connectors, let alone internal ones.
2) Extremely slow GPU. A GPU with only 128MB of dedicated graphics RAM is very slow to begin with - and is actually slower in software-only MPE mode than GPUs with more RAM.
3) Not enough system RAM. CS5.5 needs at least 8GB (preferably 16GB) of RAM if you're using a notebook with a dual-channel memory controller. Unfortunately, the MBP has only two DIMM slots like most laptop systems, making an upgrade to 16GB relatively expensive due to the higher cost per GB of 8GB DIMMs.
4) As we all know, OSX's multithreading performance is relatively slow compared to that of Windows 7.
In other words, there is not much that you can do with that MBP, as far as inproving the performance is concerned. Even if you can locate a Thunderbolt external hard drive, you're still stuck with the low-end discrete GPU that eats up more CPU cycles than most due to the insufficient amount of dedicated graphics RAM.
I feel your pain. I'm a MBP user with FCP. My laptop is quite older then yours, but... When I recently decided to switch to CS5.5, I also opted to switch back to PC. It makes more business sense. More powerful system for a lot less money. But more importantly, PremierePro shines with Mercury Playback Engine. So, unless you get a MacPro with a Quadro 4000 card, your out of luck on a Mac. And as RJL stated, CS5.5 runs faster on a PC, mainly due to better multithreading performance. Perhaps Lion is a tadd better then on Snow Leopard?
I used to think that I "needed" a laptop to edit. The "convenience" of transportability to client sites made it attractive. But in reality, I edit 97% of the time in my office. So I can now get a desktop that is twice as powerful as a laptop. In addition for the same price, I can get twice the power from a PC then a Mac. So in essence, very roughly speaking, I get 4 times the performance on a tower PC then a Mac laptop for about the same price. So for me, it makes a lot more business sense.
And yes, I'm a diehard Mac user, and love it very much. Mind you, I'm still keeping my old MBP for home and office apps.
if you insist on keeping the apple you will need to get an external thunderbolt raid array
but you will still not be able to take advantage of the MPE due to the crappy video card in the latop (ATI)
ideally send it back and get a windows system (laptop or desktop) thats build for video