The Marriott website promotes the Melbourne Marriott as being a 5 Star boutique hotel. It is very good with really helpful and friendly staff, excellent staff, but by international standards I would put it at 4 to 4 and a half stars and not boutique.
My room had an adjoining room and was not noise sealed which meant that conversations and alarm clocks etc were far from private. Other than that was well laid out, spacious, comfortable, reasonably well lit and adequately equipped. The curtain didn't close properly so it was not possible to fully darken the room during the day.
The shower taps are on the other side of the water stream, ie you have to get wet to turn the water on, which is ok if you are the one taking the shower but they are separate taps rather than a thermostatically controlled mixer so it is going to be too hot or cold while you get it right - not very 5 star. Also the mirror is not heated so it will mist up, again not very 5 star.
One of the things I have got used to in 5 Star hotels is some kind of music system, I didn't notice anything in this respect. Obviously there is scope for disturbing the neighbors but it would be handy for drowning out the noise from an adjoining room.
As for 'boutique' the Melbourne Marriott does not meet any description of boutique that I can think of. To me a boutique hotel is usually on the smaller side, have some distinctive attribute of luxury and very importantly will have a notable character or charm. As far I could see this Marriott was a normal hotel from the outside and on the inside.
Finally I would really appreciate hotels leaving a note as to whether tap water is drinkable or not - how are international travelers to know otherwise. Of course we can ask but a statement by the hotel is more reliable.
Would I stay there again? Yes.