You know... I filed my wife's N400 last night and today it has already auto generated two documents. One being the receipt, and the Second document being the biometrics reuse document that we all had to wait a couple weeks or so to be sent to us after filing the I751. Tells me everything really is online and if the system can determine the reuse of biometrics, then just how backed up are they that they have to manually go through everyone's files just to make a decision? I know my wife is currently down my throat asking me if I am lying to her about her immigration because one of her other friends filed their I751 after we did (Her friends is also LIN like ours is) and apparently got their 10yr in the mail recently, so they all think I am lying to her. lol
Well, at least the N400 is easy to file. Just make sure you have everything accessible that you basically used to file for the K1, AOS, and ROC combined, and it is pretty smooth and just need to update certain documents. lol