I also found them a little bright initially – not too much, but it was noticeable coming from P3ESR and SHL5+, which (in my view) are more illuminated than other Harbeths.
I felt that the sound fleshed out a little more over the first couple of weeks. I'm always a bit wary of this and believe it's more about getting used to a new sound but in this case, I'm feeling confident there was a change with a few miles on the clock! I have now moved home, and now in the smaller room they were intended for (moved from 5.5 x 4.5m down to 4x4m), they sound warmer and darker, but equally lovely. They're very nice at low volumes also, retaining plenty of detail.
I once had P3ESR in this smaller room, and always wanted a bit more sparkle. I have spent time and money swapping speakers and boxes to get a bit more openness and 'in the room' sound, without going loud. If I had the Falcons a few years ago, I think they would have fit the bill. Still, nice to try different designs through the years.
I still rate the P3ESR a lot – and as mentioned – they really come alive with a bit of volume and power and do very well in larger spaces compared to many mini monitors. They don't get shouty. I'd love to try them side by side with the Falcons when we eventually move back to a larger space, with no neighbours, and give them a good bake off.