As you can see here

The number of botnet clients using the Tor network is still around 3.5 million, but the next picture shows that overall network performance is getting better again:

Browsing .onion sites like the hidden wiki is still slower than usual, and often sites dont load at all.

What you can do is:

1. Dont use .onion.to and other web proxys, install the Tor browser bundle from torproject.org

2. If a site fails to load, hit “new identity” in Tor/Videlia and then refresh the site, after it loaded once its usually working fine.