if you have ttl metering that is capable of spot, center, and matrix metering, then you should be well off.
incident meters are good if you are a stand still photographer who shoots stand still subjects in forever even lighting.
a tech junky who should shoot more than do math may jump in and argue the 12.5% gray vs. the 18% gray issue, but it doesn't mean a rodent's buttocks if you know how to make a one time slight adjustment to exposure. reality is that most ppl couldn't see the difference.
i've owned 2 handheld meters. i gave them away. if you don't have spot metering ttl, a handheld spot meter would be a nice addition.
to each his/her own, though.