The most significant attacks against Tor users have been done via malware; Even when additional security measures such as "Gap" is used in addition to Tor. What is the state of the art technology to defend against these attacks?
The best defenses against malware are, first, keeping your systems patched, and second, being wary about what you give permission to for running under your account or under a superuser (administrator/root) account.
An adversary targeting Tor users specifically may go after Tor Browser Bundle components. If you keep your Tor Browser Bundle updated, you will likely not be taken over through the TBB by most attackers.
If an adversary first has an 0day exploit for TBB or other software you use, and second, is willing to take the chance of burning that 0day by using it, then you are at risk. Think on your threat model, and make your decisions accordingly.