Just as an example, I re-opened this thread (which loaded quick), and selected the link for page 2 of it. That took just over 50 seconds to load.
I haven't noticed any issues with other sites using the same proxy servers - one is actually a 'backup', and is very lightly loaded.
I'm probably nit-picking, however 50 seconds just seemed a long time to load, especially when compared to yesterday. Let me know if you need my proxy server public IP address as a reference if you are checking logs etc (I'll PM them to you). I must admit I haven't tried any other browsers as of yet.