no, there are compatability issues. for example, most of the internet is designed for ie5. difficult truth, but the truth never the less. macs can work around this mostly, but it will be stumped. try getting on sony's music store, for example (they have exclusives i'd like, sometimes). one of many. my printer is not certified to work with a mac. it does, but it wasn't easy. and it's the most popular epson in the shop (C46). other peoples memory pens will not work on your mac, unless it's specifically FAT32 (most defaults are NTFS). MSN novelty bits don't work on macs - i'm always having to say "sorry, got a mac lol"...
To dismiss that one of the mac's major failings is compatablilty is a bold, and ultimitaly a wrong statement.