Hi, all!
I know that this thread is fairly old by now, but, in case anyone is
still interested, CastleCops seems to be responding well at the moment, and has been for about the last 36-48 hours.
I'm keeping my fingers crossed, hoping that it will stay that way!
Up until last Friday, whatever link I clicked on, I'd get several page load errors, network timeouts, etc., but if the Firefox status bar ever got past "Connecting..." to "Waiting...", I might still have time to go out, have a full English Breakfast, do my morning shopping, come back home and eat lunch, by which time the desired page
just might finally have loaded!
However, since around late Friday evening or early Saturday morning (in Sydney, Australia), the site's response time seems to have improved almost to pre-2007 DDoS levels!

Several CastleCops admins/regulars have
denied on their forums that there has been
any DDoS attack in the last few months, stating that the slow response problem lies with hardware and/or software. (I know that they need new server hardware, but then, why have the response times improved now? The progress scale about their drive for donations for the new hardware they need has not changed for several weeks, and they seem to be still about $USD11,000 short, which suggests to me that the new hardware has not yet been acquired).
Anyway, it's working well, now, which is
great for me, because I've recently been getting
hundreds of spams with malware links, which, of course I've been religiously reporting to MIRT.
Just my 2 cents' worth.