I’m a fan of preconstructed decks, especially some of the non-intro products Wizards has been putting out. However, I take a different approach than Jay. I like to customize, tear apart, rebuild, refocus, and repurpose what I pull out of those boxes.
Sometimes I like to retool decks into easier-to-play, more-consistent versions of themselves, so that I can hand them to new players and explain them quickly. Other times I like to tinker with decks and fill them with bomby, splashy cards that make for lots of fun. Once in awhile I like to optimize for the kill. Either way, I feel like personalizing preconstructed decks is a great way to make them more interesting and more fun, utilizing some of the basic framework.
One of my favorite preconstructed decks in the past year was the Duel Decks: Phyrexia vs the Coalition set, because I loved that storyline and was thrilled to be able to play as Urza and Yawgmoth, re-enacting that climactic battle. Then I played the decks.