I recently returned to Bangkok for a 3 month stay. I had read mixed reviews online about the Nantra de Comfort hotel, but having some familiarity with the Thonglor area (which is nice) and noticing that the price included an inexpensive option for breakfast, I decided to book a short trial stay. I opted for the budget room, so I can't really comment on the other types of rooms.
Pros:
1) Breakfast is served between 7 and 10 am. Coffee and water seem to be available 24/7, though I didn't avail myself of this.
2) The hotel is in the middle of things just off a busy street. You can easily walk to and from the BTS, even with your bags. (I did so twice with two large rolling bags.)
3) It has a nice TV in the room, if that's your thing. I rarely turn the TV on, even during a long stay.
Cons:
1) The room is so small as to be claustrophobic. With the exception of the little nook where the bed is placed, the room is less wide than the length of the bed.
2) There is no closet, only a small bar by the bed to hang clothes. I would say it is perhaps 2 feet (60 cm) wide. There is no dresser so you are forced to live from your suitcases. And unfortunately, there is no floor space for your suitcases.
3) The aircon, which is cold, is located at the foot of the bed, so it's blowing in your face all night. I didn't like this, and solved this problem by reversing my bedding so that my head was under the aircon and it was blowing on my (covered) feet.
4) The toilet seat was broken, so that you had to sit v-e-r-y c-a-r-e-f-u-l-l-y to avoid sliding off onto the floor.
5) The towel rack was broken, so whenever you used it, it would fall apart. It could be manually fixed, but every time you removed your towel, it would fall apart again.
6) There is no window in the room--except in the bathroom. Be careful leaving that one open, however, as mosquitoes will join you in your room.
7) The walls need repainting.
Now outside the room
8) The breakfast is only toast and cereal and fruit coffee, tea and water. The first day I woke early and went down thinking breakfast started at 6 am rather than 7 am. I sat down at a table to wait and watched them finish setting up the breakfast before 6:30. No other activity before 7, but I had to wait. (Though I didn't ask if I could start early. However, the receptionist also didn't invite me to go ahead and start.)
9) The receptionists don't speak much English and haven't been properly trained in customer service. When I checked in, they gave me two key cards, but didn't tell me what they were for, so I had to try to figure it out for myself. (One gets in into the separate budget building and your room. The other enables the electricity in your room.)
I tried to figure out who the "target audience" is for this hotel. I decided that for backpackers, this would be a perfectly fine upgrade from a hostel. For most people, however, there are better options out there.