Looks like, with the new FTB modpack, they included Thaumcraft, which looks interesting.
World Edit:
One good reason for World Edit would actually be to copy peoples' houses, and paste them onto a plot of land on a new world after a wipe. It also comes in pretty handy for repetitive actions like building a bunch of detailed walls or something. You can build one, set markers, then copy and paste the wall piece wherever you need it. Of course the wall example is just that, a quick example. It can be done with anything. You can also mark a plot of land and convert that plot instantly to cobblestone or something. In the case of your hollowing out of mountains, you could have marked a cubic area and replaced the existing material with block 0, which is air, and that would have done that job in 30 seconds instead of hours. I find making a good circle or cylinder to be nerve-wracking, especially when building a tower. With world Edit, you can //hcyl 6 20 1, which is the command to make a perfect hollow cylinder, 6 blocks in diameter, 20 blocks high from where you are standing, and create it out of stone, which I believe material number 1 is.
Mo Creatures:
I like what it adds. We get more mobs, good and bad. We would get horses to ride, tigers to tame and have escort and protect us, more sea life besides just squids, like sharks, mantas, dolphins, etc.. I think it would add nice variety. Creepers can destroy just as much as ogres, so I don't find that to be a valid argument. yes, I have played with Mo Creatures, and I liked it.
Op:
When I play minecraft, I play because I like to build things and show my work, as well as check out what other people are doing. The server is not a competitive server, so I see no reason why people can't enjoy the game the way they like. Having grown up with everything from Capsella, to Erector sets, LEGOs, Robotix, and more, I really enjoy being able to just build away and even create working circuits in Minecraft. I also like to build high. Without the levitation of op mode, I constantly die. I know, you are supposed to hold shift in order to hold onto what you are standing on, but with my disability, it is just difficult to keep constant pressure on like that. I hardly ever play FPS games anymore because I just can't keep up and compete anymore. Besides, I like to float around what I am building to make sure it is looking right. Another nice perk is being able to continue building during day and night without having to get shot down from a scaffold by a skeleton. Often times, when I am not building a project, I actually go to survival mode to explore.
Some fun mods:
1- Trapcraft
2- Jammy Furniture Mod Who doesn't like to decorate?
3- Tropicraft It is a new dimension based on the tropics, with new materials, mobs, and items of that theme. You can also get a pet monkey!
4- Dayz Mod I just found out about this.. Looks interesting...
5- Dynamic Mazes looks fun, but then I can make mazes too.. :)
6- MCMMO would add classes and the ability to raise skills and much more, like an mmo
7 & 8 InfiCraft and Forgotten Nature. They add lots of decorative blocks; woods, stones, slabs, stairs, carpets, fences, and other decorations.
You just have to check out the links... So awesome!
http://www.minecraftforum.net/topic/521617-125145-inficraft/
http://www.minecraftforum.net/topic/1519278-forgotten-nature-mc145v112major-addition-to-nature-in-mc/
9- Zepplin Mod You build a little airship, plane, or whatever, separate from the ground, then add a control block. It then recognizes your structure as a vehicle, and you are able to fly it!
10- Ships & Boats Mod Similar to Zepplin, but for boats, and it even has working cannons!
http://minecraft-mods.org/ships-and-boats-mod/
Anyway, just some mod ideas...