The whole "so many pre-orders you may not get a copy" line is so BS.
GameStop ships to each store enough copies to cover 1.5x the number of pre-orders. So if they have 10 pre-orders, they get shipped 15 copies. 20 pre-orders? 30 copies. It's a formula that they always follow, except for the biggest of games that they know will have extra long legs, then they'll ship even MORE copies (particularly Madden - that's a heavy walk0in title). So if they have a lot of pre-orders, you're MORE likely to get a copy if you haven't pre-ordered.
Now, for niche games like Atlus's stuff, you probably wanna reserve. But even then, I remember our store got in like 6 copies of record of Agarest War (the big box with the mouse pad and everythign) despite having maybe one reserve. We couldn't find a way to sell 'em all.
Reserves are totally unnecessary these days. I only do it for the free shit.