The problem isn't power users. The problem is that people adapt to features. It's extremely difficult to remove a poorly thought out feature after the fact. People will complain, whether or not they're power users. People are change averse, even when it's just skin deep. When it changes their workflow, they're going to scream bloody murder.
Edit: There are very good points being made about knowing your target audience, designing for simplicity, etc. But in the end, if you change your user's workflow, they're not going to be happy, even if the end result is a better product.
That's the source of the mentioned complains in the support forum. They're complaining because something they used to have isn't available anymore.
It's only natural that they feel angry and betrayed. If the direction of the product's evolution really is removing those features, it should at least be done more gracefully. For instance, first disabling them for new users but maintaining them for current customers. Or releasing a new "light" version and giving the customers the option to stick with the old one.
Edit: There are very good points being made about knowing your target audience, designing for simplicity, etc. But in the end, if you change your user's workflow, they're not going to be happy, even if the end result is a better product.