Proper OS10 progs aren't meant to have a memory allocation, the system sorts the memory according to what is required (the fixed allocation was an OS 9/Classic thing now 8 years past). The thing about PSE is that once it has grabbed the memory it needs, it holds on to it even though you have closed all the files you were working on, expect CS is the same. Its nice if you go back to a file you finished with and find you can still do 'undos' but otherwise a bore.

Having had a play with your Powerbook i was impressed, opening and rendering D50 files on it was so fast where on this pc it takes 3 times as long.
The only problem i had was the keyboard, but that would be easy to get used to if i was using a mac enough. It did take me a while to get used to the slightly different keys and the single mouse button but i got there in the end. I never did get my head (or should that be fingers) around right clicking but i guess that would come with time.
If i had not got a new Windows laptop for free recantly and had the money i would have seriously considerd a Powerbook.

I always recommend mac users to get a Kensington mouse which has 2 buttons & scroll wheel and can operate on the 4x3 flat surface to right of touch pad which it disables. Of course not all progs make use of right key, but the scroll is there and you program the key combs for favourite short-cuts (pocket mouse pro with either retractable cord or cordless but that loses a USB port)

The laptop I have is a 2GHz Core2Duo Intel MacBook, probably as powerful as the mid range PC's of the moment but slowest of the current MacBooks. It does run NX very well perhaps 50% of the speed of the Macpro. The keyboard is a new design with flat tile-like keys, probably designed not to trap any dust or debris in between the keys and is easilly cleaned.

I use a mighty mouse (Apples latest mouse) with a scroll button that allows scrolling around an active window which works in NX.

Previously using a PC I would have to choose the 'grab/hand' tool to move around a 100% view photograph, using a Mac with a mighty mouse I simply move around with the scroll button leaving NX with the cursor.

The mighty mouse can be used on a PC see link -> http://www.apple.com/mightymouse/gallery/wired_480.html

Photoshop is one of those programs that runs faster on a PC or on top of Windows. When looking at performance benchmarks between PC and Mac photoshop always run twice as fast on a PC. The primary use of a Mac for me is converting and editting RAW files in Capture NX, something it excels. I guess photoshop with its memory allocation is not good for OS X and if anyone shoots JPEG only and prefers photoshop that a PC is best for you.

Strange - I run Photoshop on both platforms - and for me the Mac is a LOT faster. I run a Mac Pro quad core at work, but even on my Macbook Pro with 2Gb RAM, CS3 beats the pants out of my P4 3.4Ghz PC with 4Gb RAM.

You are right, I must have been looking at comparisons using CS2 or via some virtual machine. The CS3 test below shows Mac beating PC on all tests except for initial opening -> http://hansv.com/cs3/

The problem with CS2 on Intel based Macs was that, not being a true binary application, it has to run in emulation mode via Rosetta.

CS3 is a whole different kettle of mackerel! :)