My recent AirPortr pick-up in an 8-9am slot happened at 9.15. Luckily I could cope with delay, but if I'd been in a rush...

Not sure the check-in element adds a lot, but might give a bit more breathing room if tight on time. Now having the pick-up like with the Scottish flights into LCY would be much more valuable!

ETA - now if they could bring back some form of central London check-in that would be great. I like HK for this and also used the KL Ekspres service recently