You don't really need a copper pot to make toffee and caramels, but yes, it does make a difference. I first made caramels and toffees with revereware, and with the toffee it seemed that scorching was always a risk. I did experience a little smoldering on one toffee batch, but it was minimal and the toffee was still good. Any quality pan that conducts heat evenly will work-if you already splurged on the all clad, you don't need to run out and get the copper pot.
My copper pot sits in the attic with my chocolate tempering machine for most of the year, so do what makes economical sense for you. I bought mine with the $150.00 an eccentric venture capitalist gave me for coming to his house and fixing a flat on his bike when I was a bicycle mechanic at Wheelsmith. Thank you, Bernie!
If you do splurge for the copper, be sure to get some good copper polish. Avoid anything that smells too much of chemicals like Brasso or Noxon, as these could impart bad odors to your candy. I currently use Bon Ami, a powdered polish, with some satisfaction. If you don't rinse it off right away, it will leave little streaks. I once had a paste copper polish that was applied like shoe polish that I liked a lot (Penny Brite?), but I couldn't find it in local stores. You can also make your own polish with flour, salt and vinegar.
You will want to polish your pot before putting it away for storage, but you don't have to polish between batches. I enjoy watching the vivid red and purple colors deepen after each batch of caramel or toffee. I tooks some pictures but they didn't do the vivid colors justice.