I tend to use it, but its a timing issue. In my experience, when C&R dealers buy large lots of stuff (P1, P64, M57, TTC), they buy them pre-sorted into G/VG/Exc condition groups. If you buy early and check the hand select box (no special instructions, just paying the fee), they just toss you a box that says Exc on it. If these are gone, they toss you a VG. When there are only Gs left, they say things like "hand select" probably isn't worth your time.
This system seems to be interrupted if you give SPECIFIC instructions (e.g., I want a P1 from the 80s with the hex bolt and thicker slide with serrations in front of the safety) as now the dealer has to look into some boxes.
So, the earlier you buy, the better condition your hand select is likely to be...and the more likely you are to get your money's worth. Paying at the end will just get you the best of the Gs.
YMMV