So I played with the new iMovie a bit this morning. Some early observations:
-It copy/upgraded my old iMovie library (non-destructively) to a new iMovie library so that it was compatible with the new iMovie 10. I let it do this overnight so I'm not sure how long it took. But it was a while. . . probably a couple hours? (I probably have over 100 "events", maybe a few dozen "projects")
-The "iMovie Library" seems to be more like iPhoto Library now, in that the folder is now a package instead of a regular folder. (Have to right-click and choose "show package contents" to see what's inside.)
-All my projects are also visible in the "Theater" tab, but they were NOT automatically uploaded to iCloud. Instead, when you click the Theater tab you see all your projects represented by a thumbnail (not unlike looking at a bunch of movies in iTunes), and there is a little "upload-to-icloud" icon in the upper right corner of each thumbnail. I uploaded a couple to my "iMovie Theater" on iCloud and they upload no problem (after a significant amount of time which is I'm sure dependent on your file size and bandwidth). But just thought it was interesting that the upgrade of my iMovie Library automatically grouped all my projects into iMovie Theater, but didn't automatically upload any of them to iCloud.
-Instead of a Projects window up top and an Events window down below, now there is just a single side bar on the left that lists events, and folders containing multiple "projects". After the upgrading of my iMovie Library, I noticed that all the events were preserved as events, and the projects went into an item called "updated projects" (which itself was among the events on the lefthand sidebar). When you click an event, you see the clips in the lower right window as usual, with the ability to preview/scan them with your cursor. When you click "updated projects", you see multiple projects in the lower right window, represented as movie/film thumbnails. Double-click on one of those projects and you get a new window structure showing the clips contained within that project in the lower window. Haven't tried dragging clips to/from projects yet, so not sure if that is different now (since I don't think the project and event clip window are open at the same time?).
-I tried importing some new AVCHD video from a camera archive. It imported just fine, but it wasn't "instantaneous". But I think it was less time than it used to take in iMovie version 9.x. (I guess I was expecting that the import would be near instantaneous since the update claimed native AVCHD support, implying to me there would be no transcoding.) I still haven't dived into the iMovie Library to see whether importing AVCHD means it is just copying in .mts files into the library package, or if it is converting/re-wrapping them as something else.
-Importing successfully from a camera archive was a win in and of itself, as the last time I tried to do that in iMovie 9.x, the import failed after the first 5.5 seconds of footage was imported. . . even though the archive was created by iMovie itself! Never figured out why that was happening, but I'm pleased as punch that iMovie 10 doesn't have the same problem.
-The default is for the iMovie Library to be stored in the "Movies" folder in your user account. As soon as I can I'm going to try and move that to my external HD. And learning from past mistakes, I'm going to make that move entirely inside of iMovie. Do NOT do that in the Finder. (Doing so with the previous version of iMovie somehow induced a bunch of visual artifacts in most of my iMovie Events clips; ie: corruption in the AIC movie files. Something I now will be able to correct by re-importing the original AVCHD from the camera archives.
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Regarding graphics card requirements:
To run iMovie 10 your machine must have an "Open CL compatible graphics card".
Here is a list of cards that are compatible. You can go to everymac.com and (or just go to "About this mac. . ." on your machine's Apple menu) to see what card your mac has.
I'll just mention that I have a 2009 17" Macbook Pro Intel Core 2 Duo 2.8 GHz and so far the skimming/scanning/previewing of video has not been choppy at all. I'm impressed because I was expecting it to be, but everything has been pretty smooth. Though I have gotten the spinning beachball a couple times when I moved from an event clips window to a project clips window.
http://support.apple.com/kb/HT4664
NVIDIA
GeForce 320M
GeForce GT 330M
GeForce GT 640M
GeForce GT 650M
GeForce GTX 660M
GeForce GTX 675M
GeForce GTX 680MX
GeForce 9400M
GeForce 9600M GT
GeForce 8600M GT 128MB (Note: OpenCL compatible, but does not meet system requirements for Final Cut Pro X, Motion 5 and Compressor 4.)
GeForce 8600M GT 256MB
GeForce 8600M GT 512MB
GeForce GT 120
GeForce GT 130
GeForce GTX 285
GeForce 8800 GT
GeForce 8800 GS
Quadro FX 4800
ATI
Radeon HD 4670
Radeon HD 4850
Radeon HD 4870
Radeon HD 5670
Radeon HD 5750
Radeon HD 5770
Radeon HD 5870
AMD
Radeon HD 6750M
Radeon HD 6630M
Radeon HD 6490M
Radeon HD 6750M
Radeon HD 6770M
Radeon HD 6970M
The following aftermarket graphics cards support OpenCL in Mac OS X v10.6 Snow Leopard, OS X Lion v10.7.x, and OS X Mountain Lion v10.8.x:
NVIDIA
Quadro FX 4000
Quadro FX 5000