Pretty nice, since Tor is full of feds 
Hi Ufonautas, we live in a post-Snowden era
which proved that we, tin foil hat ppl
were not crazy but very much on the right track.
More than that, the reality got past the imagination: the NSA has built unbelievable systems .. "PRISM", "Turbine", "XKeyscore", "Turmoil", ... (1)
it is like an evil twin of google+facebook on steroids
Anyway, Snowden leaked that the NSA is trying hard to break Tor (2) (cit. There is no evidence that the NSA is capable of unmasking Tor traffic routinely on a global scale," the report said. "But for almost seven years, it has been trying.)
but to date, they are only able to trace a given target (cit. We will never be able to de-anonymize all Tor users all the time.)
and it is an expensive and time consuming 'feature'.
Snowden himself were using Tor (the 'Tails' linux distro) and Lavabit for emails
and the NSA wasn't able to violate them (3 and 4).
Back to the feds, take the Silkroad example: there were no real hacking / big brother involved in finding the Dread Pirate Roberts (5) (cit. it didn't take technical back doors to find him; it just took a lot of solid detective work, some subpoenas, and a search engine.)
You may also notice that the number of Tor relays and exit-nodes didn't unexpectedly increase over the last 18 months:
https://metrics.torproject.org/network.html?graph=networksize&start=2013-01-01&end=2014-06-22#networksize
In short, it all depends on how dangerous you are and how big you want your enemies to be.
1. http://arstechnica.com/information-technology/2013/08/building-a-panopticon-the-evolution-of-the-nsas-xkeyscore/
2. http://arstechnica.com/security/2013/10/nsa-repeatedly-tries-to-unpeel-tor-anonymity-and-spy-on-users-memos-show/
3. http://www.engadget.com/2014/05/01/tails-linux-os-version1-0/
4. http://gizmodo.com/try-the-super-secure-usb-drive-os-that-edward-snowden-i-1563320487
5. http://arstechnica.com/tech-policy/2013/10/how-the-feds-took-down-the-dread-pirate-roberts/
and some other links to cheer up this nice sunday
http://arstechnica.com/information-technology/2014/03/nsas-automated-hacking-engine-offers-hands-free-pwning-of-the-world/
http://arstechnica.com/tech-policy/2013/08/nsas-internet-taps-can-find-systems-to-hack-track-vpns-and-word-docs/
http://arstechnica.com/security/2014/03/nsa-hacker-in-residence-dishes-on-how-to-hunt-system-admins/
http://arstechnica.com/tech-policy/2013/06/use-of-tor-and-e-mail-crypto-could-increase-chances-that-nsa-keeps-your-data/
http://arstechnica.com/security/2013/09/majority-of-tor-crypto-keys-could-be-broken-by-nsa-researcher-says/
and in general: www.arstechnica.com/series/nsa-leaks/