I've recently upgraded two different machines from 5.4.2 to 5.5 Precise.
These are frugal installs.
In both cases the upgrade seems to have gone smoothly (although as usual desktop shortcuts disappear) with the exception that on every subsequent boot Puppy still displays " Updating ... layered file system ... next boot will be faster" (although the actual update is performed - correctly - only on the first boot with the new system - the subsequent ones appear to perform a check only)
I've noticed this in the past with previous version upgrades, but in those cases removing fsckme.flg from /mnt/home also removed the problem.
With this version, fsckme.flg seems to be being recreated at every boot and triggering the "update" .