I have the rapha polartec alpha gilet (the older, pro team one that was a closer cut than the brevet).
Honestly the only issue is when to wear it. It’s so bloody warm. By that I mean that the issue is that it is like 3 steps of warmth in and of itself, so it isn’t a very good ‘on and off’ piece – it is either cold enough to wear the entire time, or way too warm to wear for longer than the first 10 minutes of a ride.
The only time I can think it would be appropriate really is over a Gabba or Softshell at -5-0deg. Or, maybe, on a long slow ride where it’s cold enough at Z1, but you take it off for a single max chat effort then put it back on.