A good sine assists in the creation of nice soft waveforms, moves you
away from the buzzy, sharp square/saw paradigm, allows you to create
classic "glassy" sounds, sounds with resonances, soft tones, sounds
not easily copyable. To achieve a cleaner sine out of my oscillators
would require me to dedicate a filter to waveshaping. The triangle is
also not a buzzy waveform and seriously, I'd be happy with a perfect
triangle and wouldn't mind of my sine was imperfect. Analogue Systems
VCO triangle gets near perfect. Plan B Model 15 has the perfect
waveforms IMO. It just doesn't track as good as I'd like. So the point
is, it's absolutely possible for a VCO to meet my perfectionist needs.
I'm guessing and hoping that Tip Top Audio VCO has a perfect triangle
(no buzz) and I'm also guessing that its sine is not buzzy either,
just harmonically rich... but I'd need to hear a frequency sweep to
really tell.