> in what way has it gone uphill versus just using Debian?
Their lawyers' willingness to risk shipping pre-built zfs kernel modules (that are always in sync with the kernel). Pretty important if you're into that sort of thing, it's easier to remove cruft once post-install than to keep an eye on DKMS for years (making sure that it hasn't disassembled itself and continues working).
In the early days it had a differing and usually better aligned release schedule for the critical graphics stack.
As a function of time, you are increasingly likely to get rug pulled once Shuttleworth decides to collect his next ransom.