I'm nearing the end of Broken Moon, and converting to 4e as I go. A few quick things come to mind: Be careful with insubstantial in the prison, we were all pretty tired of chipping away at half damage by the end of it. You'll have to put some thought into how to handle haunts - Open Grave has a chapter about haunts, and I put a few of them into the framework of a skill challenge that dealt damage like a monster. I made all of the five notorious prisoners into solo monsters, which felt pretty fun every time they knocked one down. I used a heavily re-fluffed Astral Dreadnought (turned down about... 20 levels) for Father Charlatan... he sadly never managed to successfully trap anyone in his pocket dimension.
Don't be afraid to change things - I was making the conversion very literally in the second book, and ended up using an elite or solo nearly every combat as a result. I'm much more satisfied with the approach I've been using for the end of Broken Moon, asking 'how do I make this feel like 4e in Golarion'. Sometimes it means opening up the maps and adding extra terrain features. Sometimes it means adding or subtracting monsters, or giving the Demon Wolves demonic cohorts, or using the stats for Divine Boons to represent the Harrow Card rewards. I'm looking forward to statting up Raven's Head as a 4e artifact!
Read some of the more recent 4e adventures and try to figure out what makes them tick, mechanically - then translate the essence of the Pathfinder adventure into that framework.
