In the past, I've really rated Siteground Hosting very highly, and recommended them to anyone asking about US Based dedicated servers (Heart would be my first choice for UK Based Dedicated Servers or VPS). Unfortunately experience has worn me down.
To be clear, I'm not, and never have been, a Siteground customer. However, some of the people I do some work for are, so I occasionally have to escalate things to Siteground, or step in when Siteground have asked their customer to take some action.
I've been quietly sitting on some of these frustrations for a little while, but in the last week some have been added, tipping the balance in my mind.