Vasoconstriction is bad, as it reduces bloodflow/delivery of Oxygen/removal of CO2 and less protein/nutrients are delivered to cells. That's why we take NO-whatever products in the attempt to vasodialate and get more bloodflow into our muscles during workouts.
Nicotine causes vasoconstriction in smaller vessels (apparently, not the heart or major vessels ( circres.ahajournals.org/cgi/content/abstract/62/5/891 )).
However, it does vasoconstrict the smaller vessels (important to us, the thousands of tiny ones that wind around our muscle cells).
I smoked/dipped for 16 years, and before I quit, five years ago, I was getting "ringing" in my ears daily, likely from years of reduced bloodflow starving the nerves in my inner-ear...until I quit all tobacco...and haven't had a ringing problem since. (There was a Japanese study done on hearing loss in smokers that indicated reduced bloodflow, but I can't find the reference right now).
Is dipping "that big of a deal" to your workout? Probably not...especially to you young guys...but it does appear to have a negative effect overall.
-hp