The hotel is in/connect to the Copley Place tower and parking garage. You can park your own vehicle and take the mall elevator to the main mall level and walk a couple minutes to the hotel lobby. If you don't need to be taking your vehicle out during the day then this is significantly less expensive (although still a ripoff) to park it yourself.

Yes this hotel has an M Lounge now. I haven't gotten to experience it yet, but supposedly it is open weekends so you eligible elites should have access from status benefit.