Okay, so, here's some feedback. Been playing for a few days and I'm more than satisfied!
This modpack is just perfect. I've been looking for a good stable (it literally never crashed/froze) pack with aquaculture/agriculture and Pam's harvescraft (jesus, approx 400-500 food items - prepare you cookware and ingredients, also SMP fishing contests are really fun). It's basically a perfect mix of all four popular mod types - worldgen (with a bit of adventure, would use some dungeon/battle towers/etc mod), industry (Rotarycraft is incredibly amazing, so is any pack containing it, also TE3. Maybe a bit more of these? Just no old boring stuff like IC2/BC, please :c ), magic (Ars Magica, Blood Magic, TC4, Witchery (best one so far, really fun), arcane scrolls, etc) and finally farming. The latter is incredible there, and it's also still useful even if you're not into food farming (Magic Crops!)
A bunch of other mostly "random" mods like Gany, Random Things, and Extra Utilities is also a nice touch, as always.
Now about some... downsides. I guess I can suggest mods here?
Bibliocraft.
Or Carpenter's Blocks.
Or better, both.
But ideally, the first.
Why? Well, on my server, I've set up a nice underground brick kitchen with Agriculture and Pam stuff, but it feels so empty w/o Bibliocraft's chairs, tables, and shelves.
I'd like to put all of the useful stuff like salt and other common ingredients on shelves, put plates on table, put mod food on them, place nice looking lights (along with ProjectRed ones) on ceilings and walls, set up a library with bookshelves, brewing room with potion shelves, an apartment room or a house with customizable Carpenter's Blocks doors/trapdoors/beds/slopes/slabs/collapsible blocks, etc.
I know I can always add them myself, but I like having some good mods already in the pack, by default. Not only it makes it better for everybody, but also my fellow server visitors don't have to bother to manually add them themselves.
Well, that's it. A bit more mods-that-pretty-much-nobody-ever-played-with (I see quite a few being already in the pack, awesome) and a furniture mod to match with alive atmosphere mods like Agriculture.
(...I had to build a stairs sofa... Jesus christ, I haven't done that in quite a while...)
And how about Mariculture? I guess it should work fine along with Aquaculture, while making oceans/lakes a more interesting place. Another good example of an atmospheric mod.
Hope you can excuse my poor English.