Breakfast Topic: Alts in Mists of Pandaria

Back on November 20, Lead Systems Designer Greg "Ghostcrawler" Street tweeted the following:

This got me thinking about my own alts, and it's been spinning around in my head for a few days now. I was online on Saturday, and most of my guild were too, principally leveling alts. We're just getting started with raiding, having had a few people afk at the start of the expansion thanks to holidays and house moves, but even those folks seem to be prioritizing alt leveling over smashing out the gear grind on their mains. And I kept thinking about Ghostcrawler's tweet.

Mists is designed to be compelling without alts. As someone who PvPs, end-game content hasn't ever really been a big problem for me, although I did put a stop to Dragon Soul and Firelands raiding after a point. So at the end of Cataclysm, I had some time on my hands, and like everyone else I leveled some alts. Not that many, mind you, I only had six level 85 characters at the end of Cataclysm. But I liked it! I really enjoyed having alts. I liked that, if there was a raid that called for one tank, I could easily switch onto my shaman and heal, or my priest and heal or DPS, or my mage, and so on. I liked that all these characters were decently geared, and that I could perform fairly well with all of them. And I liked the variety.

So I'm wondering if Blizzard's philosophy here is actually a bit wrongheaded. Is it good to have alts, or would you rather just have one main character if there was enough to do? Are alts only there for when you're bored, or are they a vital part of the game? I lean very strongly towards the latter, but how about you? And do you have alts?