I have been trying to find a replacement for ACDSee for Macintosh. I hate iPhoto because it lacks any useful editing tools and it forces you to import all of your pictures into your iPhoto library on your local drive and tries to organise them for you. I like ACDSee because it functions as a photo viewer as much as it does an organiser.
Thus began the quest. Quite a while ago I checked to be sure that there wasn't already an ACDSee for Mac, and there wasn't. They made one a long time ago, back in 2000 I believe, but I 1) can't find a place to obtain it, and 2) don't want something that old that probably lacks the features and stability that I like in ACDSee.
I got the demo version of Aperture 2.0, but it still rubs me the wrong way. It still won't function as a photo viewer, only an organiser. Although it allows you to leave the photos in their current location, it still forces you to create an Aperture Library on your local drive that gets fairly large very fast. This is not helpful on a laptop.
Another product I have demoed is Picture Arena. This is a nice programme that I liked. It is an excellent Macintosh version of ACDSee's viewing and organising features, but it lacks any editing tools. You could use Photoshop for any editing, but the you have two programmes doing the job of one, and since I would have to boot into Parallels to do that anyway, it isn't really worth it. Thus it also falls short.
There are a few other programmes out there I have yet to try; the next one up is Photo Mechanic. I will post as I figure more stuff out.