Photo editing software that works on Lion?

I'm a recent switcher, have a Mac Mini running Lion. It's been tough finding substitutes for all my PC software but I'm getting there. One of the things I can't find is a Photoshop equivalent. I've got GIMP and would love it if it worked consistently, but sometimes it won't work at all, and since I edit photos for my work, I need something dependable. Here's the problem: I laid out quite a bit of money for my Mac Mini system and would like to find something either Open Source or very cheap. Suggestions?

I bought Adobe Photoshop Elements for Mac. I love it!

Other options would be; Aperture and Pixelmator. Both are available on the Mac App Store.

Here is a recommendation from a post by one of our Forum members. I have not tried it myself, but you can't beat the price.
Seashore

Pixelmator is probably the closest to Photoshop, and a lot cheaper than PS Elements (which is another fine program). Basic editing is more than accomplished in iPhoto, and for some reason a lot of people overlook the venerable GraphicConverter these days.

In short, there is a wealth of fine photo-editing programs for Mac, depending on how extensively you tend to edit photos and how much you want to spend.

As another newcomer to mac I had the horrors of not being able to afford to replace my beloved photoshop cs4.
However I have found new elements contains a lot previously missing from elements (including , importantly , full layer mask support). Plus if you buy the software rather than downloading it. you get both mac and windows discs ,just in case you ever decide to decamp back to windows, (gasps of horror from dedicated mac users everywhere! )

I posted the original query. This to report I ended up with Pixelmator - not free but certainly cheap at $30, especially compared to hundreds of dollars for Photoshop, and I'm quite pleased with it so far. Best thing about it is that it does some things BETTER than Photoshop. For example, when I use the crop tool, it shows me pixel dimensions as I move the outline, which my version of Photoshop doesn't do. Useful. And Pixelmator works fine with Lion so far - so many graphics/photo programs I've tried don't. I found Pixelmator because of suggestions here, and thank everyone for their suggestions.

Postscript

In my Mac newbie clumsiness and ignorance, I didn't know I had iPhoto, mainly because I didn't see anything that told me I had to activate it with my Apple ID. Today I discovered that. Big DUH! Anyone else still looking, if you didn't know you have iPhoto, now you know. Go to Apple App Store and click on Purchases. A window will come up telling you to activate several apps by entering your Apple ID (at the moment I forget what the other ones were). That's the ONLY way I found out iPhoto is bundled with Lion.

Between Pixelmator and iPhoto you should be able to do pretty much whatever you like with your photos on a non-professional level. I love iPhoto, and I use Pixelmator every day for quick-n-dirty graphics jobs.