I don't have a problem with reputation grinds in general. What I disagree with is then using that reputation as currency and having to regrind it. Basically Warframe's reputation grind boils down to:
1. Make a faction like you.
2. Steal from the faction so now they like you less.
3. Make them like you again so you can steal more stuff.
I honestly prefer it if once you had max reputation then that's where it stays forever and you can buy things with ... I don't know, the stuff that's actually used as currency (for Warframe that's credits). I realise that's basically replacing one grind with another (grinding reputation vs,. grinding credits) but as long as what you want to buy isn't priced ridiculously high then it's not that bad and at least you can get credits from doing practically anything in the game and you're not forced into doing bounties/fishing/farming sentient cores/toroids.
This is just my personal preference at any rate.