I messed around with CP/M on my 128. A friend had a TRS-80 and we could exchange programs on floppy w/out any problems. Those [link|http://www.devili.iki.fi/Computers/Commodore/articles/A_Look_Around_the_1571/|1571 disk drives] were slick, could handle numerous MFM disk formats besides Commodore's GCR.