The reason why sparkle never worked is because there wan't an update watcher. You had to run DellEFI before it'd check for an update which is basically pointless, because it's a run once and forget about it type of app.
NBI won't have that feature (mainly because, well, it's kind useless). Sure, I could modify the Apple updater to check with a server run by myself, but that's just not very clean. It'd work, but that has a dependency on a third party server that might not be up forever (and trust me, it'd go down plenty of times).
Anyways, as Mechdrew said, NBI will auto run after an OS update which should take care of most issues (although I'm want to make the kext patching happen at boot time, that way NBI doesn't need to run after each update...)