I've used yahoo, espn, myfantasyleague.com and cbs sportsline, and for me cbs is the best and easiest to navigate.
CBS is NO DOUBT THE GOLD STANDARD when it comes to Navigation. They got it right. No argument. If you're an owner, and you could care less about other things beyond ease of use, you'll LOVE Sportsline.At the same time, CBS has HORRIFIC customer service. Communication is truly horrible. CBS ultimately demonstrates they don't care about you as a customer, IMHO.
CBS has consistently had SERIOUS issues in early weeks of the season just staying up and accessible.
The live scoring while very fast often misreports plays, and doesn't correctly assign points.
Issues often occur in-season and aren't fixed in a timely manner.
CBS has not improved the product significantly over the last X years (plug in your own X).
And yes, CBS is more expensive than just about anything else.
If you're a Commish, this is the LAST service you want to use. If you're a demanding user, this is simply not the best option.
Outside of my opinion about not caring for Customers, the rest of this stuff is well documented. Just because you haven't had these problems, doesn't mean you won't. I've used most popular fantasy services out there, free and pay, in multiple sports. I personally believe in working with businesses that value me as a customer. From this perspective, there are plenty of better choices out there. I recommend MFL and RT Sports. XPertleagues also seems to have a fine product, but they are not as established (yet).