I upgraded pretty early on.
With that said, you might be able to get rid of a lot of your Revives (if you're not fighting enemy gyms constantly) and as you get higher you could easily use lots of simple potions healing just one of your pokemon in order to bring your item count down.
However, I still do all of those things and benefit from having the larger bag.
To me, it was worth it. I horde items in whatever game I play. I'd rather not have to spend a bunch of time worrying about it in this one.
Fenrir---------------------Svetlana-------------------Blaine
Mmm, this IS a tasty burger!