It's a lot of fun to do. You get out of the house and have a good time learning the basics.
But there is a big cake world out there that doesn't include Wilton so don't go crazy buying Wilton products. Most of them aren't very good. I highly, highly recommend looking into getting Americolors gel colors to color your buttercream with. And Satin Ice fondant is great to work with if you get to that point. Also, look into buying Fat Daddio's or Magic Line cake pans. The Wilton pans are pretty flimsy. Using quality pans like the 2 I mentioned will give you better results.
I've been decorating since 2000 and enjoy it. I took what was the equivalent of the first 3 classes and have learned the rest on-line or with a DVD series that I adore:
http://www.sugaredproductions.com/
Sharon is an awesome instructor. Her fondant dvd made a huge difference for me after watching it just once. I had fondant experience but her tips and tricks put my work to another level.
Another biggie-invest in an oven thermometer-less than $5! Very important to make sure your oven is running at the right temp!
Have fun!