I've had it for a couple of days now, but there are a number of things about PE4 that make the transition from version 3 to 4 needlessly difficult, not to mention if you get PE4 first.
The main change involves the use of "Bridge" to handle what the Browser function did previously. Unfortunately, it seems there are some missing planks in their Bridge, as it's like having 2 separate programs attempt to talk to hand off files to each other. It is clunky, not intuitive at all, and often doesn't work in a consistent way, even when you figure it out.
According to Adobe Technical Help [when you can reach them through 3 or 4 layers of sales beforehand], there is no "Organizer" for Mac that comes with the Windows version, and they were surprised at a number of missing elements in this version as a result. It also seems that they've tried to piggyback an existing full Photoshop program--Bridge--onto the back of Elements, which despite appearances, is a completely different program.
Another example: the Adjust Shadows/Highlights--which allows you to correct for things in shadows, or too bright...buried in a 3rd level menu...has been changed from the PE3 default of "50% lighten" to a "25% lighten" with no ability to change that preset. So everytime you want to adjust your picture, you have to push the slider back to 0% and start out there to see what's best for your photo. Clearly Adobe recognized their 50% preset was too much for most, and changed it--but left off the ability of the user to preset what works best for us. What's the solution to this or any other inflexible/confusing issue? I was told several times that if I wanted things to work better, I should buy the full Photoshop.
That is simply unacceptable, especially for a company of Adobe's size and history of working primarily on the Mac platform. I would rather have fewer features that work more reliably and straightforward, especially involving putting our most used features on a toolbar instead of being forced to grab them out of deep menus everytime.
In Bridge, they are trying to combine a number of features found in iPhoto, such as rating photos by stars, making it more flexible. However, they don't allow you to customize your displays or views enough to be efficient, much less easy to deal with. The speed of Bridge, and especially interacting with 4, is slow. Also particularly irksome is the lack of sensitivity/responsiveness of the sliders within PE4, i.e. brush size and opacity.
So far, I'm not impressed with the Magic Selection Tool, one of the main reasons I wanted to upgrade. It doesn't seem to grab things as efficiently as advertised, although it is better than just the Magic Wand 3 had. I'm also less than impressed with another new feature: Adjust Skin Tone, something that could be a big time saver while offering the improvements most people care about.
The combined Help program is overly detailed in some regards, yet leaves out big chunks of the program for you to guess at solutions. They have virtually no tutorials or overviews of the program specifically for the Mac version.
I will update this review as I use it more, but I would caution against jumping at this upgrade until they work out more of the kinks in the interface, unless you are a virtual pro and don't mind spending a lot of time figuring things out that aren't quite Ready For Primetime yet. What I look to PE for is something that allows more extensive editing than iPhoto6 has, and yet doesn't have the complexity or cost of the graphics standard Photoshop.
Whether because of the Mac platform changing to Intel chips, or friction between the companies, it seems Adobe is heading in the wrong direction on the Mac platform, making us seem once again like the red-haired stepchild in the computer world, while still charging the same as the Windows versions.