You know when you are faced with using somebody's crappy bit of code but you could just write the whole thing from scratch? But then you'd have to 'splain to the boss man why you spent all that effort doing by a totally different way? And the client will be pissed....and the coding team will be pissed...and basically it all just sucks ass. But you can't bear to let the cluster borkage mess exist and still call yourself a professional?
Reviewing a revised NIH grant that you didn't review for the original submission is a little bit like that.