As everyone else has said. Stick with v15 and below. v15 was ROCK solid and had a damn near perfect interface that our customers loved. We went to v16 and immediately, calls, backlash, upset customers, our ticket load went up over 800% within 3 days of deploying v16. I wish we could time travel, I'd go back to before we upgraded and not do it. SmarterTools really needs to sit down and think about v17. As far as I am concerned, no one was asking for a new interface, we have over 20k users and not one of them was asking for a new interface, though many many other feature requests have gone unheard or simply ignored / declined by ST. We lost customers after upgrading to v16 with complaints about the interface, said SM was now confusing to them etc.
Even managing the spool (for example, we had a spool backup due to Cyren going down) trying to manage ~20k+ emails in spool turned my Chrome into lagged mush, v15 never did this. We've had complaints from customers about it making their browser feel slow or use tons more memory. Still get complaints till this day infact.
We are almost 6 months into SM v16 and still no documentation etc. on this fancy new API that v16 was pumped up for and a brand new interface that frankly is a massive leap backwards. IMO and most of our users, the only good thing about v16 is the new meetings system. I fear the API simply will not get any documentation done on it since ST is so busy with bug reports and *HOPEFULLY* a good mapi / outlook connector solution.
Just look at the differences in the changelogs...
v16 has 675 "fixes", 52 "additions", 102 "changed" and 22 "efficiency" for a total of 851 changes
v15 has 258 "fixes" 42 "additions", 20 "changed" and 5 "efficiency" for a total of 325 changes
v16 so far is more than v15, v14 and nearly v13 combined in terms of total number of "changes".
Of course with the new interface, it is to be expected, but we are only six months in and v16 is still getting fixes and improvements so the number will continue to climb. We will stick it out and upgrade to v17 when it comes out, as really, we cannot go backwards from where we are now!
Stay where you are for now Todd :)