It's all right. I prefer ESPN's set up to any other format I've been involved in, as it's the most user friendly when it comes to presenting the info you want and need easily. I liked NFL.com's set up as well, although I'm not in any leagues there this year. Yahoo would be third. It's functionally pretty similar to ESPN but I find it doesn't always work right. Sometimes I'll set my line-ups and it will say it saved them, but when I check again the changes weren't saved. This has happened numerous times this year, although I've always caught it before it fucked me over.
Flea Flicker is functionally pretty solid. What I like about it is that setting line-ups is pretty easy, and you can make multiple moves at once before saving. Searching for players on the waiver or from other teams is as simple as it is anywhere else. What I don't like is that you typically have to click on a player and go to a totally separate page to see basic information like game by game scores, injury updates, expert recommendations, etc. It's not like ESPN and Yahoo where you just click the player and a little blurb pops up with almost everything you need. They do have those blurbs for some players, but it's usually just a single sentence of text about the player and not terribly useful. For reference, I currently have three players on my eleven player starting line-up with blurbs, and one of them is my fucking kicker.
What Flea Flicker seems to excel at, though, is user customization. You can set up leagues just about any way you want, which is likely why it's preferred for dynasty formats. I didn't set this league up myself, but it's obvious you can do a lot of things that you can't on ESPN functionally. If you're looking to set up a dynasty league or a league with a bunch of keepers, I'd consider it. If you're just doing a standard or small keeper league, I'd stick to ESPN or Yahoo since Flea Flicker doesn't really do enough differently to set it apart from those two.