I've been playing around with it for a week or so and while its nice, I can't really understand what it does that iOS 5 can't (other than weather/calender) on lockscreen.
Information on lock screen. Fully customize the notification center. Collapsible sections. Refresh mail accounts right from notification center. Add notification center addons and tweaks right on your homescreen. I use Calander pro on my springboard and then underneath I have two rows of icons and then the dock. Gridlock and folder enhancer give me a one page springboard neatly organized and looks cool. I am a heavy calander user so i love that NC addon and love it even more because I can use it right on my springboard. Lockinfo helps pull all of this together. Plus I like how Lockinfo is so customizable and themeable. Makes for a much better looking and more useful notification center.
Obviously this is just my opinion. This is why I use lockinfo. I hate how the stock NC does not have collapsible sections! Drives me insane haha.
Edit: intelliacreenx is a tremendous tweak too. I just prefer lockinfo because for my needs, it offers more. But I know people that swear by intelliacreenx. You really can't go wrong with either one. It just comes down to personal preference and needs. Hopefully this helped clarify things a bit when it comes to LI or IX.