Sadly, being limited as I am to services available in the UK, I couldn't make this article as comprehensive as I would have liked. I'd have liked to have included Rhapsody and Pandora, especially the latter as I still lament the day it closed its doors on the UK, but I sadly can't.
Nonetheless, we still have a great variety of services to choose from in the UK. If you haven't just skipped to this page (in which case shame on you) you'll have seen me show my cards in terms of what I consider the best of the bunch when it comes to streaming services. However, I'm going to temper that conclusion a bit here - with good reason.
If you're looking for the most comprehensive service on offer and money is no object then, yes, as I have already said Napster is the best subscription music service on the market. Saying that, if Napster To Go isn't of interest and the larger library Napster offers isn't tempting enough to justify the increased cost, then MSN Music is a great alternative. It offers a library that for the average listener is likely to be no less comprehensive than its rivals, but with the lowest month-on-month cost.
I would love to recommend Last.fm as well, but its future right now is just a little uncertain. If, and this is a potentially big if, the cost of Last.fm's subscription service is equal to or less than Napster's then the added benefit of being able to access it via any web browser will make it a very compelling option. Right now, though, I can't be sure. I definitely wouldn't hesitate to recommend Last.fm's free streaming services to anyone, though.
Overall, though, the best thing is that there isn't a wrong choice, as such. Admittedly some of these services are better than others, or at the very least better-suited to a particular consumer, but all of them offer the same fundamental benefit. The music you want, when you want it, wherever you want to listen to it.
Who could possibly call that a bad thing?