I like how easy it was (and still can be) set up! The support team has been very helpful as well - they have always answered my questions promptly with clear answers so far away across time zones or during holiday seasons when there may not even really seem to exist anyone working those days/times :).
It's nice being able to use something without having an IT department around constantly managing your network setup; this makes things easier all round :) We've had no issues yet but we're using Ibass mostly just because our current provider doesn't offer what we want anymore ;), nothing specific about iBOSS itself though other providers tend towards "lockdown" mode way too much sometimes if you don't know exactly why you require certain features etc., while some others allow too many unknown ports open through default settings :(.