Really enjoying this mod so far, it enhances the gameplay in a big way. I'm using the more spawns option atm, and when I hit Vault 34 my computer started lagging in the caves leading up to the vault (normally this section is butter-smooth for me fps wise). It took me a few seconds to realise that the extra ghouls (probably around 2-3x normal I would guess on the 'more' setting?) were impacting my performance, and it became very obvious as the extermination was in progress that the framerates were getting better and better as they died off.
This is maybe one of the real 'stress-test' areas of the current morespawns esp, but it did make me wonder if its possible to set a script to determine roughly how many extra mobs are likely to spawn in a given cell, and moderate that number if it starts to reach a particular ceiling. This might help to keep things moving in mob-heavy areas. One good thing I noticed was that it seemed quite stable, bearing in mind the load. I'm running a number of other resource heavy mods (nightvision, more complex needs), and I only crashed once and that was on a reload after dying. Otherwise, it was stable albeit slightly laggy in a couple of places.
By the by, vault 34 does not need more ghoul spawns in case anyone's wondering

I burned though about 600 rounds of armor-piercing 5.56 ammo, countless 40mm incendiary rounds, about 50 odd stimpacks and god knows what else in terms of resources. It was also incredible fun, and very atmospheric with that many ghouls running around (I was playing in the dark with headphones on, and I confess to being startled more than once by mobs sneaking up behind me). I eventually got to the armory with about 2 stimpacks left, complex needs telling me that if I took another chem I'd die from overdosing, and about 5 rounds left in my gun. Easily one of the most intense gaming sessions I've had in a long time, can't recommend it enough!