I like that it is very secure, easy to use for an end user with little IT experience, quick response time when problems occur (it's not always perfect).
The admin console can be confusing at first but once you understand how things work its actually pretty straight forward after getting your head around what each section does/is used for! Support are great too - they're responsive in answering questions quickly which isn't often seen these days as support usually takes ages or doesn't get back until there’s already been some kind of issue caused by their product! Having this server up 24 hours per day 7-7 has made our life so much easier now we don't have any downtime during working times where data could potentially go missing etc!!