I used to love using DSP and NSV. It's a shame development never continued as Shoutcast used to be amazing software.
It still is. Both formats are still in mass-market use, the majority of my companies profits are (worryingly) made from the sale of Shoutcast DNAS's.
Its just Nullsoft have never recieved the backing from AOL to develop it any further. It could have contained all the features of Steamcast and Icecast had AOL not wrecked Nullsoft.
As for the IE7 interface looking "cluttered" - what a load of codswallop. Ive never even heard that from the most ardent of Firefox fan's. If anything its a breath of fresh air. The Opera interface looks more cluttered to be honest, and that has always been praised for its sleekness.
IE6 was very cluttered. Especially when you added the Google Toolbar/MSN Toolbar for things like pop-up stoppers and tabbed browsing etc... IE7 is very far from it however.