... Does this sound right?
That's right... in fact you should not
'hear' anything from the AF-S or HSM, they silently pop into focus much faster than the noisy mechanical AF gear train of older lenses...
-> The added bonus with the HSM or AF-S is the full-time manual overide which you can perform by just twisting the focusing ring without
having to change the AF/M mode switch first
BTW older Sigma 70-200 f/2.8 EX did come in non-HSM version for Nikon mount, which are slower, so be careful to get the latest 'HSM' lens only if you want to compare :blah:
Folks just love to poo-poo the Sigma's: http://www.fredmiranda.com/forum/topic/138012