Personality
I stayed at the Sofia while attending a conference at a more modern hotel up the street a couple of blocks. The modern place was plenty glitzy, but I was always happy to return to the Sofia with its helpful staff and warmth. If you like hotels with age, personality, and style, you will like the Sofia; if you like new glitzy places filled with shiney objects, you will probably be dissapointed.
As others have noted, my room could have been larger and brighter, but it served me well; it was clean, organized, comfortable, and well supplied with ammenities . When I had TV problems one evening, Jesus was on the spot within moments to take care of things courteously and promptly; the desk staff answers every question the same way. Some of the public areas could stand a little freshening (carpets, for example, in the entries), but the room was spotless and modern.
The Sofia has a very European feel about it, and I like that unique charm and style.