I was able use this software for one year without any issue from my side! The support team always responds right away when you contact them - they are very quick at taking care your queries or concerns that may arise during setup/implementation phase (I had few but it's OK).
There were no issues we faced while implementing their product as such so nothing much comes out here :) If there would be anything then its pricing should get reduced more if not completely free!! Easy solution required good knowledge about email clients like gmail etc., which most users don't have unless asked multiple times regarding what exactly do these softwares look after? And yes even Gmail does NOT offer an option where mail items can directly go through Google Apps Sync instead having another application sync mails between google apps account itself-this will save time otherwise taken up.