Now that my original Touch (N905) has fallen off the back of the firmware upgrade train, and because I was not satisfied with 2.6.1, I decided to look back through previous versions of the firmware and try an older one that I preferred.
I narrowed the options down to 2.1.5 and 1.9.17, and decided to try 1.9.17 first. I am glad I did!
Firstly, with 1.9.17 and side-loaded epubs (which always use), the text can fill the screen again
No more empty lines at the top of the screen.
Secondly, you get the progress bar with chapter marker pips back again, which I loved.
It also seems to go to sleep faster, but that might be because there are fewer books on it right now--not sure.
A downside is that looking up dictionary entries in 1.9.17 requires three taps, fewer in later firmware versions.
Overall, I prefer 1.9.17. I think it is better for customised side-loaded epubs.