It works really well with Exchange Online/Office 365 environments with a very simple setup and ease of customization and easy to use and understand management panel. Not sure how well it works on on-premises deployments as I have not tested it in that scenario.
We use Xink for every client that has a team and wants to remain "on brand" with any email correspondence regardless with whatever device they are sending from, be it phone, tablet, laptop or desktop. We setup all our Xink instances so that it is "fully server side" which means the email signature is injected while in transit and appear correctly at the recipients end. It does get some getting used to when composing emails and there is no signature but a few tests create the confidence needed.
Fortunately, we haven't had to deal with support much, but every time we have, they were very responsive and were able to either fix our problem or explain the way it worked in a timely and polite manner. Not much else to say other than being in the same region is also a plus for support.
Their primary method of support was via chat which is quite responsive and generally online. If it is outside their support time, support tickets are responded to within 24hrs. I also found the support docs helpful and relevant. They would have received a 10 if it wasn't for when we had a support query and it took a couple of different agents before the solution was found in an existing support doc. Would have though that all their agents would know their knowledge base a lot better.
We used to use Simprex, and evaluated quite a few other email signature platforms such as Rocketseed/Parrot Digital and Exclaimer. We found Xink simply worked! First time and every time. It was also very cost effective and as a re-seller being able to view all out clients in a single pane of glass was also very convenient.