I really enjoyed my stay at the Tokyo Marriott near Shinagawa as it was comfortable and I was upgraded to a lovely premium suite. The property is one lateral half of the Gotenyama Trust Court tower (the other half is residences) and is within walking distance of both Shinagawa and Osaki stations. Here are my pros, cons, and photos:

Pros:

• Upgraded without asking to the Gotenyama Suite on the 25th floor (highest guest room floor) - this didn't show up in app until after check-in
• The suite was lovely with a nice design, large living room, large dining table, half bath, small but cozy bedroom, and large shower and bath room
• Couch and furniture were comfortable
• Bed was quite comfortable with just-right mattress, plush pillows, plush covers
• Shower pressure from the wand head was fantastic (the rainfall head was not strong)
• Train noise was minimal, especially in the bedroom
• Curtains had automated controls
• Staff was very nice - walked to check-in, chatty about the weather, etc.
• Elevators had lovely touch-sensitive features
• Lounge offering was nice
  • No real tea time desserts, but evening offering was extensive with lots of choices (didn't try) and lots of desserts (did try) - they also had self-pour spirits, like Bailey's
  • Lounge staff very nice and really wanted to help
• Breakfast is in the restaurant (Dining G - best name ever) and was tasty - nice curry, made-to-order eggs and pancakes (daily special)
• Mistake credit card charge during my stay had already been refunded and refund receipts were waiting for me at check-out
• Wi-Fi is spotty, but the individual router with separate password in the room worked well (nice that they recognize the problem and provide a solution)

Cons:

• No Internet TV OS
• Only allowed 1 PM late checkout due to my upgrade (I had asked for 2) - I think this is a fine tradeoff, though
• The toilet seemed to have an issue with refreshing the water every few minutes (not sure it was flushing or something with the bidet) - had to close the bathroom door to block the noise

Overall, I would definitely return - comfortable and convenient.

Photos: