I use Full View--pretty much on a daily basis. It's a private-label version of Yodlee so it's very similar to all of the other Yodlee-based sites. I've tried quite a few and I'm satisfield with Fidelity's version.
As with all of these products, much of the technology behind it is pretty primitive (screen-scraping) so you will have occasional problems accessing account information. But Fidelity is pretty good about responding quickly to any ongoing problems (like when a company redesigns their website and the screen-scraping no longer works correctly).
If you already have a Fidelity account--or are shopping around for a place to put your money it's a good option. The Full View service is free--just make sure you understand Fidelity's fee structure to make sure you avoid any maintenance or low-balance account fees.
I happen to work at Fidelity (full-disclosure!) and have heard that Fidelity is committed to this product and plans to continue to enhance it. They see it as a "sticky" application to keep people coming back to Fidelity's website and to keep their assets at Fidelity.