I have a brief experience with the Hosted Exchange aspect of Godaddy, but in that brief encounter it was really difficult working with their Exchange techs. However, I would say that their up-time was above par.
I had helped a friend migrate from Godaddy hosted exchange to the Godaddy O365. Their website guide wasn't working out well so I had reached out. First, I was told to go ahead and add an MX record to point to the new server and then begin the transition. Well, the transition got caught up and had an issue. Mail was now working halfway and not everything was coming through. I changed it back, and they outgoing email for outside the domain had issues sending, What a mess.
Eventually, after speaking with two or three different techs we were able to begin the migrate. It got caught up again because one hosted mailbox was a separate domain and I needed to get a TXT record on "that" domain. Wow.
The total downtime was about a full work week, I felt pretty bad. Outside of my control as I followed all the steps Godaddy provided me with.