I have always used buycruises which are both internet and phone. I always use the phone. Anyway, I tried DU since many on this board use them. I usually do lots of research for my cruises and know what I want so didn't think the e-mailing would bother me but it did.
I still got a quote from them since I figured if they beat what I had then I would go with them since I don't need my hand held. But they did come in about $300 more than Cruise Planners (which I also found on this site). I did call my usual TA buycruises to see if they could meet or match the price (I book a cruise with them about once a year) but they told me that the price I had from CP was great and that they must have booked as a group sailing since she couldn't even match my price.
Maybe it is because it is the special sailing, maybe not but I would also give them a call before booking directly with DU.
Enjoy.