We go through San Juan three or four times each year - round trip. It has improved enormously over the last 25 years. The new Terminal A is very functional with many food options and a pretty good bar. Concourse B was the worst and is now being reconstructed. The other concourses are more easily accessible to each other and there are many food options within easy walking distance.
The best terminal we have ever been to is Terminal 5 at Heathrow. The British Air Lounge is spectacular and has a wonderful spa to boot. Gordon Ramsey's restaurant is first rate.
While SJU will never meet that standard, it's a lot better than many other airports we have been to and it is getting better every year.