Well, been about a week since I upgraded my Tokyo with 100psi Kenda Kwest tires and an 11T freewheel. I have used her a few times since to commute and wanted to share my riding impressions.
The upgrades were definately noticeable and substantial. The tires definately roll smoother and appear to handle better. The freewheel upgrade however was SO worth it. The gearing on the bike now feels like a full sized bike. Top speed has definately increased - I hooked up a cycle computer/speedo unit and I am hitting 21mph+ on flat ground - The 6th 11T high gear offers a good deal of resistance and I believe that 5th is even higher than the original 14T 6th gear. Very rideable and versatile now for a bike with 16" tires!
The brooks saddle also improved the comfort and rideability of the bike significantly.
The upgrades equated to approximately $80 (not including the saddle) This puts the total cost of the bike at approximately $310 including shipping - still a great value and I believe comparable to the Dahon C6