I love the old 78's and think they were an excellent, hard-use rendition of the 700 series rifles. I've had extensive experience with two of them. The first was a Dept-owned 270 which was in effect our special response sniper rifle. I never had to shoot anybody with it but I did shoot it a lot, and it fully lived up to the 8X Leupold Target-Dot scope it wore.
The second 78 is an '06 I traded into 20 years ago and it has been slaying deer ever since. My wife liked it so well that I cut the stock down to fit her, with the added Decelerator magnum pad. It's always had cheap glass on it, but it literally flattened the last deer I shot with it at about 212 yards.
The only common weaakness I have seen in 78's is a tendency for the forend to warp during our spring/fall monsoons, causing the POI to shift a tad. This is easily cured by a good dose of elboow grease and Acra-Glass.