This was our 3rd visit to Ho Chi Minh City, and we stayed at the Red Sun on all 3 occasions. It's very central so there are shops and restaurants all around, and you can walk to one of the main markets. Any trip you may wish to take can be organised by reception, and they will keep your luggage safe if you go away for a few days. Even though the receptionist was not the same on the last visit, they were all friendly and helpful.
The rooms are basic, and in ours, the fridge and air-conditioning were always in working order - no problem there. It may be true that the air-conditioning gets switched off when the guests are gone for the day, but that makes ecological sense, and it only takes a minute for the room to cool off as soon as the air-con is switched on again! We never bothered about breakfast so can't comment.
All in all, stay there if you are content with the basics and the convenient location: it's clean and good value for money.