I'm holding my breath for 0.18 now for my N800, as it is looking to be the breakthough build. I've tried a couple of the 0.17testing builds on my N800, and it is definitely not ready on those devices

I was not able to get testing4 past the initial setup screen where it requires a username, as no virtual keyboard was functional.

Managed to get either testing1 or testing2 (can't remember which) running, but it was extremely and painfully slow. Looked really imprssive though.