Personally I beat it, and then went back for final weapons(besides Auron and Yuna's which I already had). After getting Tidus' weapon, and boy a headache that it was, I'm not as focused on doing everything anymore.

I think I'll go find those Spheres to watch more plot, and maybe play the cactuar game to see the village.. Not going to do Wakka, Lulu, Kimarhi, and possibly might do Rikku's final weapon.

All there is left is a bunch of monsters who require me to beat a bunch of other monsters who never really give me anything but bragging rights.

I already beat Omega(forgot to lancet him /sigh).
And I've already seen all monster creations except for the last two originals.

It's up to you if you want to spend time in it... but like the above posters... you WILL need to completely activate the sphere grid for three people just to START being able to kill things in the arena.



After that comes stat maxing.

My Tidus has every regular sphere activated and quite a few magic def spheres from One Eye too.. Most of his stats are in the 120-150 range, and even with having those decent stats, the first original creation hits him for 46,000dmg.