I am +1 for this change, I don't have any numbers but from day-to-day usage, both my systems seem far more responsive when swapping to zram instead of swap.
I do not think it is safe to assume that zram is sufficient to completely
replace disk swap. We do not know how much RAM is actually available on all
users' machines, and the compressibility of RAM contents depends on the
individual user's workloads.
I believe having zram as a high priority swap and then normal swap with lower priority to be used when zram gets filled up might be an option too (I am not saying we should go that route, just mentioning it's a possibility).