Looks like it's up to 600 now. That doesn't tell the whole story, because relay selection is weighted by bandwidth, so if the top 600 relays by bandwidth were running Tor 0.2.4, then 90% of your circuits would go through those relays. I doubt that's the case though. The problem is that the botnet is growing faster than the number of relays that are upgrading to Tor 0.2.4. Another problem is that the botnet might upgrade to Tor 0.2.4 too.