I too decided on this path after my 2008 iMac's logic board went after 2 years & 10 months back in 2011. BTW, no AppleCare, so, yes, my fault for not covering myself with extra protection.
Since then I've bought a Mac Mini with HD 6630M graphics (& extra AC). A brilliant computer which serves me well. I've also bought a couple of decent matte monitors. As with you, due to my disappointing iMac experience & the many others related here, I won't buy another iMac again, nor any other AIO computer.
Too late for me to join any legal class action here as I sold my failed iMac to a Mac enginer on eBay for a relative pittance of just over £220.
Though I also use PCs happily enough, I'm too heavily invested in OS X to switch entirely. So in future, all my Mac buys will either be new Minis or the occasional laptop. If I want much more powerful graphics, it'll be an upgradeable PC for graphics-intensive stuff, rather than any iMac or other AIO.
Maybe I'm allowing some residual bitterness to obscure the bigger picture. But unless Apple admits to a serious problem with a certain generation of iMacs & reimburses those on the receiving end of unreasonable hardware failures, I don't care. I won't touch them again.