Q: My MacPro is running like Moses.

Direct you to the proper forum for MacBook :

How to create an OS X Lion installation disc MacFixIt

Migration Assistant Update for Mac OS X Snow Leopard

incompatible with OS X Lion

RoaringApps Mac OS X Lion Application Compatibility

How to clone your system:

http://macperformanceguide.com/Mac-HowToClone-backup.html

http://macperformanceguide.com/Mac-HowToClone.html

http://www.macupdate.com/app/mac/7032/carbon-copy-cloner

General purpose Mac troubleshooting guide:

Isolating issues in Mac OS X

Creating a temporary user to isolate user-specific problems:

Isolating an issue by using another user account

Identifying resource hogs and other tips:

Using Activity Monitor to read System Memory and determine how much RAM is being used

Starting the computer in "safe mode":

Mac OS X: What is Safe Boot, Safe Mode?

To identify potential hardware problems:

Apple Hardware Test

General Mac maintenance:

Tips to keep your Mac in top form

Safe Mode, (holding Shift key down at bootup; takes longer to boot this way so be patient), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, reboot when it completes.

Mac OS X: Starting up in Safe Mode - http://docs.info.apple.com/article.html?artnum=107393

What is Safe Boot, Safe Mode? (Mac OS X) - http://support.apple.com/kb/HT1564

Upgrading from Snow Leopard to Lion or Mountain Lion should be frowned on, backup, erase, do clean install, then use Setup Assistant and TimeMachine.

Maybe you have or installed programs and drivers that are not 10.8.3 compatible.

Maybe there really was an accident or error waiting to happen.

Maybe a sign of too full disk or bad sectors.

But first use Activity Monitor and then show or tell us what is going on with the system: cpu usage, disk, memory, background processes.

The hardware products - use to be in .sig - are often wrong, out of date, or people don't realize that they can change what shows (default, product 1, product n)

With the Pro you can easily clone, do system maintenance, reinstall even very quickly.

Clone before any update or changes of course so you can go back or dual boot the old system, keep Lion and/or Snow around.

And any Mac Pro can still run Snow Leopard if needed. 10.8.3 does seem to be ideal and adds support for newer graphic cards.

Focus on only to see if you have a run away, using excess resources, etc.

Using Activity Monitor to read System Memory and determine how much RAM is being used

Starting the computer in "safe mode":

We get a dozen notebook owners with "Mac Pro" daily so can't assume anymore esp if it is their default product.

General storage and system strategy:

Break up the system and data.

System boot drive: small fast and only the OS and apps (and home account's library, minimal)

A 120-240GB Samsung 840 SSD is great way - $100-170 - best $$ I invested.

Login loads dozen programs and files in seconds (under 10)k

All the data would be on one or more 2TB drives, possibly even in an array (RAID0)

TimeMachine to 3TB drive (350% the amount of data)

Setup a 100GB or even smaller boot partition to run Disk Utility and other programs or utilities in addition to Mountain Lion Recovery.

I wasn't focused on how much memory alone but if any one in particular is using excess amounts, or a process is using excess. All the other tabs in Activity about free disk space, % tasks.

Safari process ate up 2GB, iPhoto sometimes as much or more. I had a bad file in iTunes Media Library and iTunes would eat up everything else !

I clone my drives, and use TimeMachine.

If you are only using one drive for most everything, break that into 3.

What are the programs used? primary use? what is always open?

Whatever it is likely does not happen in Safe Mode.

Removing and disabling plug-ins and extensions.

Uninstalling 3rd party programs.

Avoiding some/most any cache cleaners etc

If you want to use TechTool Pro or others, put those on the system emergency maintenance volume and use that only when needed or part of regular scheduled maintenance like weekly when you reclone your system.

And keep versions of the system, clone from pre-ML, from 10.8.2, from 10.6.8 - and keep on a shelf and not online except if needed.

Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity

Anything in double-digit CPU is suspect.

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OSX 10.6.x and 10.7.x were both 32bit Systems, although there were both capable to be also booted in 64bit mode. In Lion Apple switched the default boot mode to 64bit on those recent Mac models and with MountainLion there is ONLY 64bit subsystem and kernel present, regardless of the age of the machine because unsupported CPUs are not supported at all, i.e. any Mac running ML is 64bit capable.

64bit makes computing faster by efficiently using all cores of the cpu and adressing straigthforward every bit of available memory ( while 32bit OSX needs to make some internal stunts to adress RAM over the 3.5GB barrier ) .

The bonus features of 64bit computing might be good only if you have lots of Ram but having less then 4GB makes it inefficient. Therefore I would put lots of memory modules into the machine, keep housecleaning , re-index the drives and see if it makes a difference.

Overall system performance on older models can not be compared to a newer Mac, that's for sure.