While i agree the customization is nice, we had some problems with them in the past. Ones that i have noticed in the community.
New players tended to not customize until playing a few rounds
Some new players would have a hard time having to locate the customize area (Yes I'm aware it said "Customize" but it's true.)
Players would choose storyline character models, zombie models, combine models, and thank god not antlion models. Causing confusion in high-stress combat situations, often causing players to be shooting at themselves. (Once again, i realize that you could see players names by aiming at them, but this is high-stress, enemies everywhere.)
Animations for some of the models we're messed up
Some of the weapons were unbalanced (I know, this can be fixed.)
New players don't know how to properly use new weapons, and with-out a proper introduction, they are left to find out for themselves.
New players would spend time wasting ammo firing a new gun to try it out, often in situations where the ammo they were firing was precious.
Even with an online guide to the weapons, few players would actually read them (especially now that you dont even have to visit the site to download it anymore.)
Also, the fists were pointless. they were basically a crowbar with less damage.