On the topic of reasonable alternative tools, Sketch[1] has started to gain a tremendous amount of traction within a short amount of time within the web design community.
I'd argue that alternatives to Photoshop and After Effects are the killer apps needed for getting most people out of Adobe's ecosystem. The OS X specific alternatives for Photoshop (Acorn, Pixelmator, etc) just aren't quite there yet. I really, really want them to be though because I've held off on upgrading from CS4 for about as long as I can.
http://www.thefoundry.co.uk/products/nuke-product-family/nuk...
Unfortunately, it's a wee bit more expensive. But I wonder if we'll see a price drop soon...