Even my buddy Tamarind over at Righteous Orbs has fallen prey to the now-popular derision of DKs: "I’ve always been aware of the WoW Political/Social Hierarchy. Raiders at the top, assorted, level 80s underneath, then twinks, then alts with heirloom gear, lower level characters, deathtards."
Don't worry, fellow DK readers, THEY'RE JUST JEALOUS because they don't play the most awesomesauce class in teh game!!!!11!!!1! Ok, fanboi rant over.
I've already posted regarding the resentment DKs have faced since their inception, some of which was based on an early but accurate perception of their being overpowered. I've argued that they're not overpowered any more, but the perception is slow to fade.
They went from the best tanks to the worst in 3.1, and are arguably in the 2nd or 3rd position now in 3.2. They went from competing for top dps to about 6th or 7th as a class. Any number of well-played 'pure dps' classes should in theory nudge out DKs on the meters at the end of the day. Sure, I'm aware of the popular Recount screenshots depicting DKs second only to rogues on the heroic Anub world first kills, but those were special fights. DKs will also rule on Onyxia, but overall, they're not OP at the end of the raid. Look at mages on Lord Jaraxxus and tell me what you see. :P (If you don't know, mages should almost double any other class due to stealing Jar-Jar's buff).
A second, and much blogged, reason for the disdain for DKs has been the plethora of poorly played Death Knights that litter the servers these days. Just this week Kyrilean posted an example of a DPS DK stinking it up. Yes, I myself have been in many a pug with the sub-1000 dps DK. There's no doubt that leveling a DK is easy mode. You can afk and get to 80 without any trouble at all.
So, what to think of DKs in general?
I'll make a plea here today to not automatically assume that DK you see in Dalaran or LFG is a 'deathtard.' Like any other class, we come in various shapes and sizes, classes, gear, and yes, levels of competence (and each of these doesn't necessarily have any bearing on the others). To assist in sorting the wheat from the chaff, you can find a guide for leaders to try to help them determine if a DK is worth inviting to a group: although I seem to remember seeing this article at MMO-Champion, when I googled it I found it at Freewowguide. An interesting read even though it's partially outdated.
In any case, like Soccer/Futbol is the 'Beautiful Game,' Death Knights are the 'Beautiful Class.' Blizzard had years of working with various classes before Lich King and DKs are the first class to be added to the game since its inception. They had the time, experience, and expertise to 'do it right,' and I think they did! They had to make DKs unique, which was indeed a challenge. But overall, the resource system, the attack mechanics, and overall playstyle of the DK are very satisfying. They're a class that epitomizes Blizzard's credo of "easy to learn, difficult to master."
My former main - my rogue - was fairly simple. Sinister Strike to max CPs, Slice & Dice. Sin Strike, Rupture. No pets, a few cooldowns.
I raided Sunwell with my warlock. Hmmmm. Shadow Bolt spam, anyone?
Today, arcane mages see 99% of their damage via two spells.
DKs, you can just walk up to a mob, mash random buttons, and the mob will fall over. You'll make it to 80 without taking forever, and you won't die much. You'll also be the 'deathtard' doing 1k dps in Heroic Nexus. To actually Master the class, you have to know how to manage two resource systems, with runes and runic power. You have quite a number of cooldowns to juggle, and you have pets. There's a lot going on, but to the person who can master all this, the rewards are great! You can do very solid single target dps. You can do amazing aoe. You can (even as dps) take a few hits and keep on ticking. You can grab something or someone and pull them over to you!
Learn your class! Educate yourself, play it well! Do your best to represent the class as well as you can.
My DK is beautiful. She's deadly. Don't hate me.