Personally, I wouldn't buy any music with DRM. Its a stupid hassle. For mp3s, if you need to pay for them, check out allofmp3.com. They are based in Russia, and its been about 6 months since I used them, but they were dirt cheap, no DRM, and no problems at all. I was worried about their trustworthiness, but tech sites around the web were saying they are legit, and you can pay them with paypal if you want. Its worth looking into! My personal favorite combination: iPod and Bit Torrent
I too just got myself an IPOD video 30GB this xmas. I love it, I have all my movies/tv shows and music on it.
You can use Itunes to buy a song. or You can use another file sharing program (bittorrent, limewire, etc.) and whatever files you dload you can load into the Itunes library and still put it into your Ipod.
iMesh has WMA like that too but I have a program that copies the song into mp3 format while you listen to it through WMP. Let me know if you are interested.
I am not sure I understand the whole "renting" songs thing - wouldn't one rather own them? I would pay 99 cents to own one, but if i had to pay monthly to rent them, i would sooner just P2P them. What if you want to share them with somone else?