A whole week of commuting is done and dusted, and preliminary results are in.
The bike is brilliant. Stiff, handles well (I'm not sure how and why, but better than the original), rolls extremely well. I've got used to the saddle, I'm keeping it. The waxed chain wore in and is silent as a mouse.
The only issue - and a minor one at that - is the seatpost, that is rotating, and, what's worse, keeps sliding in. I think I'll try to tighten the clamp just a bit. If that doesn't work, I'll try to wrap it in tape, and if that doesn't work - maybe working on it with sandpaper.
Ah, I had an issue with the steerer tube catch. I asked to put a metal one, not the plastic springy thing that the original has. They did that, but the opposing thingy was still plastic, and it was too wide for the catch. But the catch has sharp edge, so this issue pretty much resolved itself. I've ordered a proper replacement anyway, but again, it's a trivial issue.