For most clinical exams, shimming (if it's even done at all) only takes a minute or so on a reasonably modern systems, and is done prior to certain sequences (like EPI). Shimming is not nearly as important with most clinical imaging acquisitions as it is for spectroscopy. Even most clinical spectroscopy or CSI doesn't require the incredible shimming effort of a structural NMR scan.

DICOM is an open format, although very complex and full of manufacturer compliance issues. You can read the images with many different tools on almost every platform in use today (Windows/OSX/*nix/iOS/Android/etc). I think what you meant is "I don't like that the crappy software they bundle on my CD of images only runs on windows"