I checked this out like a week into my stay here to meet up with some co workers and saw that they had just enough seats for them (8 people) and none for everyone else. So that is a big boo for Heart Bar, the lack of seating. The drinks are small, but good, but overall I wouldn't mind waiting to go upstairs to their other club if the time was right, because the Heart bar is ok.
Lets say if you're meeting someone there for a drink, just two people, then yes go there, but if you have a group of 4 or more, check out the Venetian or Bellagio for a more spacious bar experience.
enjoy.