Will admit to not caring for "A Scooby Doo Valentine" on first watch and it was one of my least favourite episodes of 'What's New Scooby Doo'. Just found it too cheesy and bizarre, and also found it very forgettable not long after. Mind you, we are talking over a decade now when changes of pace weren't as appreciated by me as much as they are now. And also at a time where to me Scooby Doo and valentines didn't really go, too much of an odd couple.
On rewatch though, "A Scooby Doo Valentine" is the 'What's New Scooby Doo' episode that made the biggest improvement between initial viewing and the latest and the one that has most grown on me. "Camp Comeoniwannascareya" also improved massively. It is not one of the show's best by any stretch, but conceptually and in terms of ideas (something not appreciated or taken note of initially), despite not executing it all perfectly, it is one of the more interesting ones.
As usual the animation is bright and colourful, and there is definitely a loving valentine atmosphere created. The music has energy and groove and also liked the more romantic tones. The theme song is still infectious and adds a lot to the coolly animated intro. The voice acting is as accomplished as to be expected, Casey Kasem still has it as Shaggy. And the celebrity guest star (in the second 'What's New Scooby Doo' episode to have one, the first being Simple Plan in "Simple Plan and the Invisible Madman") is not overused or gimmicky. They were actually used very cleverly, especially in an unexpected turn of events.
The script is funny and has energy, even if it is very cheesy in spots. Daphne's reference to Sarah Michelle Gellar (who played her in the live action films) was a nice touch. Again the story does go a little overboard on the cheese and the truth is on the bizarre side, but it is a unique not seen before premise executed interestingly and uniquely.
Did like the clones and the conflict between them and the gang was a lot of fun and clever, have never this kind of conflict before in the franchise's history. The gang solving the mystery from home was a first too and just about works. Did like the look at the gang's personal lives, like where they live.
In summary, one of the episodes of the show that grew on me massively. 8/10.