that's a great point pk2 - i practice my fretless extensively to a tuner. a pro player friend of mine (packard, you out there?) helped me record one time, a fairly busy passage of 8th notes that extended for a few verses, and he was surprised, since all i played to was click and drums, and yet, after we recorded the passage, we looked at it with a good tuner, note by note, and it was pretty much in. i actually think it's easier to play that way than with other instruments - easier to hear one's self.
intonation can be learned, and highly polished, just like any other skill. i've found that playing fretted instruments to tuners shows many intonation inconsistencies there as well, and they are harder to control - the pressure that is applied to the note can pull it 5 or 10 cents sharp easily if one isn't careful. it's possible to actually be BETTER intonated with a fretless than with a fretted, it's difficult, but it is possible.
intonation can be learned, and highly polished, just like any other skill. i've found that playing fretted instruments to tuners shows many intonation inconsistencies there as well, and they are harder to control - the pressure that is applied to the note can pull it 5 or 10 cents sharp easily if one isn't careful. it's possible to actually be BETTER intonated with a fretless than with a fretted, it's difficult, but it is possible.