I like that it works with any email app so you don't have to switch between apps when switching accounts - just use one client! It's not as easy at using in Outlook but if used correctly will work well enough without too much hassle (or time).
Nothing really bad about this product yet though there are some limitations which could be improved upon such things being able get more than 1 account per device/app etc.. We're solving our problems regarding multiple emails from different providers within each application / platform we were having issues managing them all before now they can easily sync across devices & platforms meaning less downtime due system failures.