Shaping is fine for the standard Uncapped accounts (they don't pay premium price, average to medium shaping is fine during office hours). Even with shaping on during daytime, the speeds shouldn't be too bad, with the After hours and weekends the "pipes" must be opened up to give some leeway.
Obviously the premium users must get full speed all the time. {getting their full Package speed at least 85% of the time, if their line is nice and clean}.
I'm guessing by premium you mean Capped and Business. Ideally we want everyone to get a consistent experience, even Uncapped users. By managing contention through shaping, we hope to do that for Uncapped users so that can have realistic expectation of throughput on realtime services at all times.