The hate comes mainly from the privacy breach. Origin's pretty creepy as far as computer monitoring goes. This is the absolute main issue that Origin hate is based on, but all of the below fuel it further and make it a bigger deal.
There's also the fact that EA reserved some of its games, as far as digital download distribution goes, to Origin or made them unavailable to Steam (the latter for which I think they're wrongly blamed as it's perfectly ok imo that they don't want to accept Steam's DD terms)
Then there's also how shitty Origin is compared to Steam. Now, if this was restricted to the deals they were offering, that'd be one thing. Steam's been there itself. But the UI and the way it handles is absolutely atrocious and not something you can blame on it being a new application. For example, when playing Battlefield 3, I open my Origin overlay and when I close it, it sometimes "restores" Battlefield 3, immediately throwing it back into fullscreen upon clicking something, costing me some 10 seconds of downtime. Yeah, not much, but the whole point of overlay is to avoid that downtime, so it basically fails at what it's trying to do.
Now, couple those completely legit complaints with the general hate that comes with being a big company and EA in particular and you get a nice hate cake, sprinkled on top with the fact that it has Steam to compare with, which is like comparing a Yugo to a Ferari in a situation where you're not paying to choose one of the two.
There's also the fact that EA reserved some of its games, as far as digital download distribution goes, to Origin or made them unavailable to Steam (the latter for which I think they're wrongly blamed as it's perfectly ok imo that they don't want to accept Steam's DD terms)
Then there's also how shitty Origin is compared to Steam. Now, if this was restricted to the deals they were offering, that'd be one thing. Steam's been there itself. But the UI and the way it handles is absolutely atrocious and not something you can blame on it being a new application. For example, when playing Battlefield 3, I open my Origin overlay and when I close it, it sometimes "restores" Battlefield 3, immediately throwing it back into fullscreen upon clicking something, costing me some 10 seconds of downtime. Yeah, not much, but the whole point of overlay is to avoid that downtime, so it basically fails at what it's trying to do.
Now, couple those completely legit complaints with the general hate that comes with being a big company and EA in particular and you get a nice hate cake, sprinkled on top with the fact that it has Steam to compare with, which is like comparing a Yugo to a Ferari in a situation where you're not paying to choose one of the two.