I've always thought North Camp could be made a bit smarter. It's quite well used, and although it never seems to be too dirty, it could do with a spruce-up. There are often weeds and overgrown bushes, there's a random block of concrete on the Eastbound platform, and any flowers planted are generally dead. The last time I was there, the ticket office was closed and there was a broken vending machine left outside it. Not too bad, you might think, but the vending machine had already been there for six months!
The footpath away from the Eastbound platform, the situation with crossing the road and the cycle path on the other side of the road all feel unsafe for various reasons.
Also, there are no clocks to speak of, which means that you can feel a bit uncertain if you can't find your phone in your rucksack and you aren't wearing a watch... fortunately, though, there are announcements before a train arrives, and the level crossing is a good clue.
In addition, there are no buses serving the station at lunchtime, it seems.
Bow Brickhill and Kempston Hardwick. Even in the context of the Marston Vale line those two are awful, especially given the former serves a decent chunk of south east MK equating to around 30,000 people in the immediate vicinity.
Millbrook is rather spartan. It has pretty poor lighting, a completely rubbish entrance, a help point (IIRC) but no other information systems... I could go on.
The bus only comes every Thursday afternoon (or something), and, as a result, it is not in any way connected to the village of Millbrook, unless you like walking!
EDIT: Since this is a thread about "Shabbiest stations", I should clarify that the lack of a proper entrance is probably the shabbiest thing about Millbrook.