The write-up above is slightly outdated. DI radio now has five channels (or streams); those are

All streams are available in at least 128kbps MP3 and in Windows Media format in varying bitrates. The most popular streams also have lower bitrates available (down to 24kbps).

Recently, it seems DI radio, at least on the Trance stream, occasionally puts in 20-second advertisements for various websites, like trance.nu, which is sort-of annoying, but if that's what it takes to serve 128kbps mp3 audio to 5000+ listeners, I guess it's OK... I know I wouldn't want to pay for (16kByte/s*5000 =) 80 MByte/Sec bandwidth from my pocket money...