You're not forced to use Apple products to keep your music--none of it is DRM'd anymore so you can use your non-Apple software to sync it with your non-Apple devices on your non-Apple computer. It's even plainly available in the file system--and Apple doesn't even require you to let it reorganize your music files into its preferred folder hierarchy.
If Apple supports interoperability, they have a mess on their hands and they're dealing with interoperability issues instead of making a better product. If they don't support interoperability, people write angsty blog posts about them breaking whatever hackish unsupported software they were using to interface with their iPod. (As for the Pre, anything that allows arbitrary devices to pretend to be an iPhone and sync jeopardizes email account information--which can be synced to the iPhone--and is a security flaw. So I'm sure Apple did intentionally lock out the Pre. But I don't think they care about gtkpod enough to intentionally lock it out.)
"On that note I'm pretty sure Apple makes way more off iTunes than it does off the hardware at this point"
Why stop at "pretty sure"? They're a publicly traded company. It's not hard to get their financials.
Here's some numbers from their Q3 report a couple days ago:
"Apple sold 5.2 million iPhones during the quarter, producing $1.689 billion in revenue..."
"About 10.215 million iPods were sold this quarter, resulting in $1.492 billion in revenue..."
"Apple's "Other Music Related Products and Services" segment was responsible for $958 million in revenue..."
Cite: http://www.appleinsider.com/articles/09/07/21/notes_of_inter...