CF card makes a big difference
The learning curve is steep, and the menus are deep, but the most perplexing thing was of all things, playback. Changing preset recording modes rendered previous tracks unreadable and got the dreaded error message ("Can not ....") ((that's it - "Can not .... and a number")). Wave files - unreadable. 24-bit files - unreadable. No playback. You'll find the numbered error messages on page 60 of the manual.
Swapping through a bunch of CF cards, RData, 2 early SanDisks, and 2 different Kingston cards, none of them worked at all. The Marantz didn't even recognize the card and said it need to be formatted on the pc (they were alread FAT32 formatted). An 80x Transcend recorded both MP3 and .wav formats but only played back the MP3 and crashed the unit when trying to play back the .wav. I could download either type of files to the Mac and they played perfectly, just don't try to play them on the PMD671. A reboot told me the card was blank. Open it on the Mac, there were a dozen readable files. I thought it was broken and needed warranty work, or there was a screw loose in front of the controls. A 60x SanDisk Ultra II 1G card recorded and played back in all formats and solved every confusing problem.
OK, so the recorder is great. A bit complicated, but lightweight, top-notch, great quality. I'd knock it down a bit for the cheap plastic exterior, but the Sound Devices aluminum exterior doesn't rate 3x the price. And if you don't put the right brand and speed card in it, look out, it will make you crazy.