The rear seat belt sockets are a bit of a faff – they sit in little sockets, which when you are sat in the back are fiddly to reach.
Talking of buying things to overcome issues, I had to buy a tray to fit in the over large armrest bin. Otherwise things just got lost in there, £12 from Amazon on a £44,000+ car !
One thing I do find making getting in and out easier is that the driver seats slide fully back when the engine turns off – if you can remember to turn it off!