A few thoughts.
Handcuffing someone who is putting up even the slightest resistance is very difficult.
Handcuffing -properly- so that they are not too tight and not too loose is very difficult under stress.
Improperly applied cuffs can cause all kinds of additional injuries and leave you WIDE OPEN for some heavy duty lawsuits (aside from charges related to illegal detention)
If one should decide to ignore the above listed thoughts, keep in mind that many (most) of the handcuffs out there are not "up to spec" for real world use so you want to research heavily before even considering using cuffs you might have.
Finally, if you are going to carry cuffs. Learn how the pro's hide a spare cuff key and have one with you, in your car, etc. Also learn how to uncuff yourself with your spare key.
That's about all my fuzzy brain will come up with right now.