ESI is a good system for the price. Very user friendly and one of the easiest systems to program both on the user and technician side. Customers think it's great. That being said it is also one of the quirkiest systems around and their VOIP and computer intergration fall around par level. The Cisco, Shoretel, Avaya, and Nortel do a better job and are much more stable, however there is a price difference. As a technian I just spent a full day reprogramming a 85 phone site because the hard drive crashed after two years. We had a backup of the whole system, however the hard drive that ESI sent was a higher revision and cannot be dropped down to a lower revision. This was found out after ESI tech support tried two hours with ESI because they thought it could be. Meanwhile the customer is down this whole time. Also they now do not send older release hard drives so now your backups are useless if the hard drive crashes. This is just many of the annoyances of this system. If you look at all the legacy products that ESI has you'll understand why they can't keep up. Why do you have to initialize a system with simple upgrades. That means losing all your data. Can you keep any of it? No. This system is just simply poorly engineered on the backend, however it does offer a lot of great features. Bottom line you get what you pay for.