I don't know if this is hard to implement, but it would be great if the user had the ability to add streming media as a channel (mms for instance). Maybe this could be done manually or by XML from a provider or online tv portal. This would boost the, not only online TV channels, but also LinuxMCE as it would add more and more channels to it. Just an ideia....
Read up on the threads pertaining to Miro Latino2, that should satisfy your thirst for "IPTV" for a short while. Hopefully full support comes later.