My stays here (as a base-level GP member, two on points, one paid) have been just fine. The rooms on the standard floors were large (king beds) and they not a whit of smoke smell (and believe me, I'll change rooms if I smell that toxic odor). Service was great all around. The one negative was that I was charged twice for my incidentals on one of the award stays. One day after reporting it (when I was already back in the US), I received a call on my cell phone from the Accounting office, not only apologizing but explaining what had happened (the bank handling their CC billing system had transmitted my and other customer's charges twice).

BTW, there's a "back" entrance directly on the Mönckebergstraße - you enter into the shopping area, and walk through a couple of doors into the elevator lobby (as noted, reception is up one floor)