I have it on both a 2.8Ghz iMac and a 2.5Ghz MBP. I haven't done a whole lot with it yet. Just playing around a bit. No compatibility problems that I've seen.
Only surprise was the dollar exchange rate. Bought both the CS4 and Lightroom 2 upgrades together to get a $30 discount. Still cost me >$300 US, which was exchanged to $373 CDN. I miss the "on par" days.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
Damn Adobe product line is confusing - a couple of suppliers have set up specialists just to navigate buyers through the maze.
Quoted for truth. Man, you need a PHD to be able to quote people a price. Had one client who had 6 various versions of Adobe software that wanted to upgrade to CS3 now, and get the free CS4 upgrade. Half versions they wanted Premium, half they wanted Standard. Took me 3+ hours to figure out exactly what the upgrade / qualifying path was and even the Adobe rep was incorrect once. After all that, they decided to wait for now.
"Right after announcing the release of 64-bit support in the Lightroom 2 beta, Photoshop Senior Project Manager John Nack dropped a little bombshell on his blog, announcing that the next version of Photoshop (CS4) will be available in both 32- and 64-bit versions for Windows, but only a 32-bit version for OS X. The reason: Photoshop on OS X is written with the Carbon API. Last June Apple decided to kill 64-bit Carbon, forcing all future 64-bit application development on the Mac to Cocoa. Adobe had originally planned to ship a 64-bit CS4 as a Carbon app and port to Cocoa for CS5, but now the 64-bit version will have to wait for the CS5 Cocoa build.
The (relative) good news is that this will primarily affect users working on "very large files on a suitably equipped machine." The average speed bump "due to running in 64-bit mode is around 8-12%" when not "using a large data set." The bad news is that it is precisely those professional users who buy Mac Pros maxed out on RAM that will likely get penalized. It'll be a sad day when the Photoshop jockeys have to run in Boot Camp to get the most out of their Mac Pros."
i upgraded to CS4 Design Standard on my home machine. no problems.
intel imac, 2 ghz. i have no complaints about stability or performance.
there is an interactive matrix on the adobe website that i found quite useful in deciding how to upgrade. it basically just asks you what products you own and then it tells you how much it will cost to upgrade.