I've been using it since it came out, and coincidentally have been fighting with it tonight whilst lying in bed when I should have been sleeping.
It's not really a widget tweak; it's a nice, easy way to install the "missing" iPhone apps onto the iPad. On 3.x and 4.x I'd done it myself over SSH with files I'd pulled off my iPhone, but I'd never been successful with 5.x.
Some of the apps don't scale well. You also have to have FullForce installed to make it work. The apps won't launch if it's not there, but it's not a dependency so it's easy to miss. The Stocks app looks great, the Clock and Voice Memos apps are scaled with FullForce and look a bit abnormal, and the Calculator, Compass, and Weather apps are iPhone native - but look decent if you use RetinaPad.
The thing that I've been fighting with is getting Belfry, Spire, and AssistConnect to all play nicely with each other. Without a lot of finessing, you can't install all three at one time since they have conflicting dependencies. Once you get them all working, though, it's kind of impressive - if you can appreciate having an iPad that acts like a 4S.
The best part about Belfry, as far as I'm concerned, is having a real, system integrated clock with alarms that doesn't need to be in multitasked. I still don't understand why that isn't in the iPad to begin with.