I just want to preface this by saying that I really appreciate all the hard work the devs have put into Median over the last few years. The quality of life changes are great, and definitely made for a more pleasant overall experience. Most mod makers would have long abandoned the project by this point, so your continued dedication is very commendable.
That being said, the direction the devs have taken with Sigma is not something that I agree with, or would want to continue to play. As others have said, normal and nightmare difficulties are a slog to get through. I find myself getting bored about halfway through nightmare. There's little difficulty until you get to mid-level ubers. The removal of the level 0 challenge, gift box from Griswold, and the character orb (I know these were gone ages ago), make getting to hell a chore.
For me, the sprint and level-gating mechanics detract from the mod's enjoyability. I used to love farming act 2 sewers for SUs due to the pack mob and crazy density, but the best thing you can get there now is sets. I should also be able to enter an uber as soon as I get there. While I understand the argument about trading and noob-friendliness, this still bothers me a lot. I also miss themed seasons, despite them being horribly unbalanced.
I downloaded Ultimative XVc yesterday, and I'm having a great time with it. I understand that you can't please everyone, and I have no animosity towards the devs. I also don't have as much time to play as I used to, so that also has something to do with it I suppose. I'll probably check out Sigma again in a year.
Cheers