My main concern is instrument upgrades (GPU/RPU and miles) working as advertised and not being trumped by ToDs or what have you.
Currently, there's nothing worse for me than having to sweat and babysit upgrade requests with instruments, especially at T-24 when the waitlist expires and R/RN and O/ON magically open up to allow ToDs buy-ups.
Also, although this hasn't affected me yet, get your IT in order, so award and revenue tickets on *A carriers don't get screwed up all the time. I'm tired of reading daily horror stories on FT about this.