I've tried this. Not impressed. Yeah, the graphics are great, but come on, you'll stop seeing them after a while. And the UI design is terrible. Too easy to set stuff off in your pocket, which defeats the whole point of having a lock screen. Weird that so few lock screen designer get this seemingly obvious fact.
For my money, the best lock screen replacement is WidgetLocker. I used to use it, but like all lock screen replacements it just doesn't cleanly replace the default lock screen. That makes it not worth the trouble.
Recent versions of Android support lock screen widgets, and this is where developers should concentrate their efforts. I particularly like DashClock, which has cool features of its own, and also supports plugins. Alas, too many plugin designers don't get the pocket issue. Same true of a lot of lock screen widget developers.
And you know, you don't really need that much functionality in your lock screen. I like being able to run my camera app quickly, and it's nice to be able to see the time, date, weather, and battery state with just a glance. Beyond that, unlocking and bringing up the launcher just isn't that hard, and fancy lock screens cause more hassle than they save.