Well Half Elf will tell you I'm pretty vehemently opposed to DLC. Basically any DLC I have is from GOTY editions. I bought a couple of actual content packs for Sleeping Dogs seeing as how it was a great port and stellar game besides.
And mind you I'm talking about gen-you-ine content packs not a fucking reskinned map or zomg a new assault rifle. I'd shoot myself through the fucking head before paying cash money for content any retard from 4chan could have developed in the span of one evening. Maybe I just have a different opinion on this seeing as I was PC gaming (and modding) long before DLC was around. When a game warranted new content it was SUBSTANTIAL enough to be shipped in a box to retail. There was a RISK involved in putting out something offensive to consumer standards beyond simply pissing people off (looking at you, Capcom).
Borderlands DLC is about right as the standard I would use. Meaty content. I've played Dawnguard and it was pretty adequate as well. I haven't played them (because I have the original collector editions and so don't really feel like paying any more) but from all accounts FO3 and New Vegas had DLC done right.