I was wondering, if in order to protect myself from hostile hacking, should I consider access via TOR to be OK to perform e.g. havoc without anyone being able to track my ip back?
Yes, that's the purpose of the protocol. It does suffer some risks of exposure from protocols that run on TOR... e.g., accessing a website that has previously set a cookie identifying you address from when you visited before using TOR.
Keep in mind that any traffic of yours leaving an exit node is no longer encrypted. The exit node can read and alter your traffic if it wishes.
The full list of weaknesses (or "user control considerations" if you will) is long. I'd start with http://en.wikipedia.org/wiki/Tor_(anonymity_network)#Weaknesses and go from there.
TOR's increase to anonymity doesn't not correlate with an increase in security in other forms.