Are there many junctions with through junction hardshoudler running ?
The only one i know of is solihull (j5 m42) southbound (but not northbound for whatever reason), which is handy cos i go through there on a regular basis.
I did wonder if this was a first off or long term trial and others might be introduced later but doesn't seem to have been the case.
The only real issue is i've had to develope a 6th sense as to whether the hard shoulder will be open through the junction as you have to wait until the the matrix sign after the blue junction sign to find out. and looking ahead for this you cant read the text but i've learnt that if it's a lane diagram it's open, if it's text it says "use hard shoulder for junction only" This gives me personally enough warning to adjust speeds and merge back in, only feeling marginally guilty to pulling back in front of traffic i may have just undertaken. Can be tricky in heavy traffic but then it's usually that heavy because the hard shoulder is closed, still, worst case is i come off and back on at the junction.. which can be quicker in some traffic conditions

The only other note of caution is where the onslip merges, most traffic is aware & merge ok others dont expect you to be there on the hard shoulder already (someone even flashed their objection at me once), plus the descending slip & closeness of hard shoulder lane gives you and them less time to see the traffic you may be merging with. So I always make sure I have a gap in the next lane to escape into should it be necessary.