I liked what I saw of iPhoto 6. I thought that iPhoto 5 was a rather "blasé" upgrade, and only acquired a copy when I bought my new iMac. What has kept me using iPhoto are the free plugins that I have found, for integrating iPhoto with my blog and gallery.
But now, with iPhoto 6, it looks like I actually have several reasons to upgrade to the new version. Which is good for Apple, because iPhoto is the only iApp that I use.
While the performance did seem to be pretty good running on the new Intel-based Apple hardware, I'm reserving judgement on that front until I see it running on one of my boxes. The big killer feature for me is the full-screen editing. You have to see this in action to really understand its power, but it looks like they have extracted some of the bits from their new pro application Aperture, and brought them down to the iPhoto level. It is super-easy to display multiple pictures (for comparisons) -- you can arrange them in any order, and size them to any size (that can fit on your screen). All of the editing tools (including the new ones added in iPhoto 6) are available by moving the mouse to the top or bottom of the screen, or via contextual menu.
In the short demo that I was given, I was very impressed with what I saw. I think that this is going to solve a lot of the pain that I have currently with using iPhoto to manage my pictures.
The other big new feature, photocasting, looks cool. I'm not going to use it because I don't have .Mac, but I like that it is built upon the RSS standard -- so that any RSS-capable client can interact with the photo stream. It sounds like they are just doing JPEG enclosures in RSS, which should mean that the images will just pop up in your RSS reader. I'll have to find a photocast somewhere and try it out in NetNewsWire. One interesting thing that the Apple guy demo'd is that if you try to open any URL that is for an Apple photocast, iPhoto will automatically get it. It looks like the Mac OS X URL handler is doing a regex match on the hostname for the photocasts, and redirects the appropriate URLs to iPhoto.
-Andy.