I Recently purchased both a Fathead II and an Apex 215 (Dual Ribbon Mic) for tracking on my band's new record.
Both were cheap.
I tracked a 57 safety on every guitar track, just in case, but the tracks recorded with either of those mics have won out over the 57 in every case.
Both are a worthy purchase. I haven't had the dough to pick up a Fathead with the transformer upgrade, but I will at some point to see if the difference is substantial enough to have one put in the first one.
There definitely isn't the amount of high end you get from a 57, but the guitars sit in a mix much better. The Fathead has taken EQ quite nicely when It has been needed.