Nodeka is a once great mud, with excellent coding and classes, ruined by greed. When you login to the game and type 'score' the first thing you see is:
Looking for power? See help donations.
Every time you type 'score' you will see this.
Sadly, this line says everything that nodeka is about. You cannot remort without donating, you cannot equal other player's stats without donating, you cannot practice to the same level of other players without donating, you even have to pay to change your password. Craziest of all, you get "roleplaying points" for donations, but you cannot get them for roleplaying.
On to game mechanics itself. Class balance is excellent and nodeka used to have a wonderfully balanced PK system. It still is, but donators will always beat non-donators with their higher stats and higher pool max. The overhead map feature is great, but many muds have that 'nethack' style map these days with so much more to offer. Mud wide events are non-existent. Exploration involves 'guess the obscure door name', that is the extent of any complexity in areas.
The areas themselves are low quality. The most recent area to go into the game has over 100 rooms with a single room description.
Good hack and slash if you can afford it, everything else lacks.