I get nearly 2%/h when not using the phone, and I thought this was great. It very much depends on your settings. I'm sure there are a number of services that run in the background and poll various servers for stuff, periodically - such as gmail, sms, whatsapp, weather forecasts, media services, cell reception and so on.
Some of these are configurable, so you can tell them how often to check their stuff, while others are not. I don't know how to detect which apps / processes consume battery, when we're dealing with such low usage. Which ROM gives you 0.5%/h? Did you check various kernels with Beanstalk? Possibly the other ROM you used has another kernel.
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I wasn't even familiar with this feature... Which version has this problem? Are you using the most recent one (April 3)? Can you specify one version in which it worked?