The upgrade of the 'virgin' 7.0.6 site to 7.3.4 went fine for me.
wrt Hacking; My woes in other posts I've made recently are due to the exact same issue at GoDaddy.
The hackers seem to be targeting sites that are running DNN on GoDaddy. It was why they changed my DNN instance folders to web-visible but NOT web-writable [the app cannot write or modify files]. It is also compounded by the fact that on a large file structure, the tools for changing the folders to 'web-writable' and subfolders to 'inherit' often time-out or error-out before completing the task... [I do not blame GoDaddy but only wish they told me what they were doing before I wasted so much time debugging the result. You can see my confusion and frustration in the recent posts]
I too manage dozens of sites and many hosting accounts. The hackers seem to be after only the DNN and the SMF [Simple Machines Forum] sites for some reason. I cannot say whether there is something in the DNN code they can trigger to cause the writes, but I have indeed seen and dealt with the results. The results are overwritten/revised default.aspx files and what appear to be default.htm or index.htm files laden with ads for hundreds or thousands of 'retailer' links. They are often easy to spot by date or size [an advantage to working alone is I remember what sites I change and when]. The attacks started in May. I check every site for the tell-tale signs almost every day.
I have also encountered issues where DNN instance A on a server writes files to another instance [folder] B on the same server. This seems to have to do with same-named folders or child portals [like /test or /home] on both instances [sorry, but that's as much as I can figure].
GoDaddy now makes folder copies, moves, and any archival un-zips NOT web writable by default. That is not good for DNN which writes to the file structure on occasion [or a lot during an update...]. [This makes restores of the app files from backups virtually unusable] If their user tools bomb when you try to fix the rights you just gotta call them and wait an hour on the phone. As of yesterday they were still trying to figure out why the user software tools are bombing, but they acknowledged the problem. I usually wait until late at night, when it usually works w/o error...
Bob