Nothing wrong with a side mount if it's a Jaeger or Griffin&Howe. Lots of benefits in having instant choice between the iron sights and scope. I certainly wouldn't install one on a rifle that was otherwise pristine, but if I were in the market for a shooter/hunter and two 99s were laying side-by-side, one with a G&H sidemount and the other with a decent quality top mount, I would go for the one with the side mount like a duck on a June Bug.
Don't knock 'em if you never tried 'em. The ones on my Mausers return to zero dead-nuts every time they are taken on and off. Every time. I can't speak for the other lesser brands (IMO) such as the Echo, Pachmayr, et al in that regard. There was a time when any rifle with a G&H QD side mount was considered to be state of the art accuracy-wise plus elegant to boot. That holds true today with classic rifles from a bygone era.
