I'm probably part of a significant portion of the players who also have little interest in i50 right now.. as I literally havent hopped on it at all but was playing all throughout pre-i50 beta (not at all saying it's not valuable and fun) but I am going to like legit use some vacation days and log in and not log off for at least 3 days when the server goes live lol
The benefit of i50 is testing. Not for the devs -- for me. I can compare different strategies pretty quickly in race / attribs / specs / RAs / quickbars, where after release it's going to be hours to weeks between builds, depending on how uber you are, to test different setups, let alone some RPs.
The downside is that the existing mechanics can be tweaked or completely replaced at any time, so tests have a short shelf life that might not make it to release.
I appreciate those still doing PvE testing as well. I've done a little spot checking, most notably on a mentalist playing with guards at various battlegrounds, but it's hard to have the patience to play through more than a level or two manually when /level XX exists.
The nice thing about /level XX that many might not realize is that targeting a level earlier than 50 will generate a random set of level-appropriate gear, a la the prior i30 and i40 iterations but for any target level.