Oh, my. Going from a studio to a 1 BR is what bit the add-on bug for us!
I think the difference between a studio and 1 BR is much bigger than the difference between a 1 BR and a 2 BR.
Heck the W/D alone means we can pack less (and with many of the airlines increasing their check in fee for luggage, maybe the add-on points pay for themselves!). And the extra space! And the full kitchen! And the jacuzzi tub! And the King Bed! OK, I'll stop.
Anyways, going from a studio to a 1BR is a huge step up and definitely prompted us to double our points (yikes!). My DW and I love having the King Bed and our DD sleeps on the pull out.
Heck, I go down to WDW once a year for a vacation with my DD (now 8) and I'm thinking about moving from a studio to a 1BR next year because of the above reasons.