It's a replacement for AdBlock. JavaScript is not blocked unless it's part of an ad. The Easy Privacy list is part of uBlock by default, so there's some effective overlap with Ghostery but they're still different.

µBlock does have an option to disable "first-party" and "third-party" scripts. It's configurable globally and per-site (per-site takes precedence).

I don't think it blocks Flash. I let the browser to that anyway, so for me this isn't a problem.

There are lists available that block the same things as Ghostery. So yes, it does replace that.

Not NoScript, though.