I joined yesterday because custom biomes drew my attention. Upon joining, reading and accepting the rules and going out of spawn, I found things like these:
The typical look of the Tundra biome:
The forest biome with hanging sugar cane:
Deserts with palm trees and weird cacti:
The whole world is made out of nice, custom biomes. The only problem I found is that some ores were not generated (ruby/emerald and uranium) or - according to the owner - generated in biomes which I have not stumbled upon yet after more than 1 hour of searching.
What makes the server more challenging (and that's a good thing if you don't want the standard Tekkit world) is the fact that not all ores spawn in all biomes. For example you can find coal and copper in Forest biomes but no coal at all in River or Plains biomes. This makes the player explore the world and have different digging sites for different ores. There also is a custom "Sky" biome in which the only mob spawns are Endermen and which additionally has a black sky (like in the End).
A big thanks for those biomes to the staff!
Apart from that, the server offers the standard repertoire of plugins (mcMMO, Towny). Towns do not cost that much to create, but have a high upkeep that can currently only be met if you vote or if you sell diamonds to the server shop. The owner - mjclone - is aware of that problem though and plans to extend the shop and also add an arena that offers paid fights. He seems to be very active and cares for his community, addressing problems and not ignoring them unlike some other servers owner out there.
The only feature advertised here but I didn't see ingame are the Slot machines, which isn't a big issue for me.