I stayed at HI City Centre earlier this year for 4 nights. Literally 50 metres from where the Finnair bus drops you if catching that from the airport (~6 euros one-way).

Room was fine, not huge by any means but large enough, although the aircon was a bit feeble, to the point where I thought it wasn't working. I mentioned this to reception and the lady spun me some yarn about 'green' aircon that works sort of imperceptibly - I let it ride as it was borderline, though I still have my doubts about the story. Carpeted floor in the room entrance, giving way to 'Scandinavian-style' wooden floor in the main body of the room.

I'm PC Gold and the only 'benefit' I recall getting (not that I was really expecting anything at all) was a discount voucher for the restaurant (about 8 euros I think). The restaurant is only OK (and they overcharged me - I did not let that one ride ) - if not for the discount I probably would not eat there. Buffet breakfast was included in my rate and again, was adequate, nothing special. On a side note I saw a man at breakfast with three plates each piled about 6 inches high with various foodstuffs. He had as much at that one breakfast as I consumed over four days.

Wi-Fi was free. Cannot recall if there was any concierge service. There is a sports bar around the corner which was very quiet during the day and ok for a couple of refreshers during the afternoon.

As you might expect, there was a sauna, though I did not use it.

I seem to recall housekeeping being extremely late one day, such that I was doubting they were going to do it, though in the end they did (without prompting).

Overall was OK - a fairly typical HI experience.