I have a customer who has f5 load balancers (mulitiple VIP's with upto 16 nodes). The are using Round robin as the allocation method.
What are your experiences when changing this to least connections or any other options?
The answer is it depends on whatever works best in the environment and a few other factors.
Take a look at F5's KB: BIG-IP system load balancing methods to see which is better suited for the environment.