Hey I just finally got all the parts for mine yesterday, and just now I found the case - happy happy joy!
About the IC: It's the heart of the oscillator, if they switch at different speeds (for example) that would change the shape of the waveform (which is a really unique one, there's a picture on Ray's site) which may or may not be noticeable...
On the soundlab electromusic.com forum they were saying that different transistors in the VCO sound different and to try different types to find your favourite. Talking of which: Did you guys use the 2N3904 or a replacement?
Building is the new bending!