Ill first start by saying I have rented an ark server and was never disappointed with the service.
Now with my gripes.
1) Server down time. - After every update or patch to a server you never restart them so my server can be down for hours. Today is a good example where the server was down for at least 8 hours before I was able to get it back on.
2) Lack of information on when servers are going to be updated or even an email saying "Hey did some tweaks or bug fixes on the servers. You may consider starting it"
3) The known bugs not being ironed out in a timely manner - This one I know isnt G-Portal but is really Funcom but how hard is it to get the MOTD working?
Anyway thats my 1 1/2 cents