Well, I just picked up a matched set of 603's last week. Gave them a try last night, XY (stereo bar) on a Taylor acoustic guitar. Given that it's a hard thing to make a Taylor sound bad, and the guy could play, the 603's sounded nothing short of amazing. I could not believe such a great sound was coming from a set of mics barely costing $200! Thanks Harvey. You certainly speak the truth.
BTW - last night was actually an experiment - not just in using the 603's, but in the way I miked the performer. It was a "live in the studio" set, so I had to deal with bleed, etc. For the vox I used a Rode NTK pointed slightly upward to decrease the guitar bleed. For the guitar I used the 603's in XY, well below the Rode but pointed down at the guitar to reduce the vocal bleed. The thing is, the 603's picked up A LOT - as everyone says - they were almost omnis (I even had to use a poper stoper on them b/c they were too sensitive to the vocal plosives). I had never done a three mic live performance setup where the guitar mics were XY. Usually a two mic (one vox, one guitar) setup works fine - I've also played with an M/S configuration to catch both gutiar & vox, but never tracked any serious work like that. Anyway, everthing sounds great in the mix - absolutely no phase problems whatsover . . . between any combination of the three mics. The 603's really shined.