It is good to build friendships. U can get groups dancing together (with one sim as dj) and all sims will become best friends quickly whilst still getting xp as the relationship grows. (you'll see xp bubbles appear as they dance). Once all sims are best friends, you'll just get the normal 30exp per sim for dancing. Other than that, i havent found much use. For the club other than if u need to fulfil sim needs quickly without using lps as a cupcake (the expensive drinks act as a cupcake). So i would say u can do without the nightclub, i regret spending lps on building it but have only houses left to add.