Being a bit of a laggard I only just upgraded my Mac to Mavericks a few days ago. If only I'd known they had fixed the number one most annoying thing about iCalendar in OS X I'd have upgraded ages ago.
Yes, you can now delete an event from your calendar without notifying the organizer. This has caused me serious pain in the past. Events sometimes arrive to the wrong email address or get accidentally put in the wrong calendar and previously you had to just leave them there for fear of sending a stupid "Steve declined your event" type email.