I'm also a Mac user, and that might not be helpful to Dogmeat, but perhaps sharing my experience would help someone, whether they're new or experienced pixelers.
Mac: Classic: Photoshop 3.0.5: While this is a regular Mac OS product, I still use it constantly. Provided you had a Mac and were using Classic (be sure to streamline your OS9 System folder for better performance), this would be my top suggestion. It may lack some of the features that those pixel oriented PC apps have, but it's still one of the best configured photoshops, surpassing a handful of descendants to the Photoshop line: Later versions of Photoshop became less pixel friendly and wonked up the layers, channels, and mask accessibility. While current versions have fixed some of the layer/mask/channel accessibility, they have become more buggy and are still not as pixel friendly as they could be. Adobe Image Ready, I am told, is a good web/pixel friendly tool with some animation features.
Photoshop 3.0.5 supports hotkeys: Type m to select the square selector tool, shift+m to turn it into a circle, z for zoom tool, f to toggle backdrop/screen modes, i for eyedropper, etc... If you've ever used Photoshop, you would likely expect the same functionality in an older version, and this one has it.
Filters for this version of photoshop might be lacking (Photoshop 5 and up might be good to use as a secondary graphics tool for more filter support, but is hardly as lightweight/portable as a pre 4.0 photoshop, based on system and HD space requirements.), however do not underestimate the power of the force!! Built in image adjusters in this program are incredibly versatile. Flaming Pear has a handful of free and necessary tools that are supported, such as an alpha transparency solidification tool to help with conversions to png (not supported, but GraphicConverterX is a great assistant for web prep). The filters I use quite often tend to be selection and mask based, such as blur, sharpen, unalias, KPT Find Edges Soft 2.1, and others. This program is competent. I used it to create some OSX icons before I even had OSX, and they turned out great.
Mac: Classic: Gifbuilder: Better than some, but still a somewhat no-frills animation tool. I adore it, actually. For some reason, the OSX version is broken on my machine?? Again, there might be a good Adobe alternative, but hey, those cost money! This is just a dependable support tool.
I wish there was a good OSX pixel app solution, but frankly there isn't one. Although I did do some graphics work for Pixen, that was before I had an OSX system. Although I do run Tiger now, I would not use Pixen: Due to bad experiences with the developers, I do not support their efforts.
Mac: OSX: GraphicConverterX: It does have the tools to do basic pixeling, and it is the tool I like for converting between formats. Has some filter and adjustment tools as well. It also supports gif animation.
Mac: OSX: Iconographer: Alright, if you don't mind working on icon sized stuff, I suppose this is an interesting alternative. It has pixel grid toggle support and several other features... and if you're going to be doing icons, I think it's invaluable, so it's worth having anyways!