I went from 1.10 (1370) to 1.30, then 1.40, then 1.41 and never lost any data.
I also ran the garbage collection tools and my maximum thoroughput went from 180MB/s to 225MB/s and the minimum went up from 55MB/s to over 80MB/s. The average went up from 110MB/s to over 160MB/s.
The only downside were that FSX and PowerProducer sensed hardware changes and asked me to re-activate them. (No problem, I keep the passwords.) iTunes also asked me to locate my iTunes library. After bootup to 1.3 Vista said it was installing a device driver, but it didn't for 1.4 or 1.41.
So the whole thing went very well!
I'm pretty sure that only upgrading to 1.10 from an earlier firmware (e.g. 1275) would wipe the entire drive.