I also LOVE Intro!!!! Several of my agility students, who are more than ready for competition, but who are hesitant to start trialling, as many of us were when we first started, have done intro in VT format at our training facility successfully. This is exactly what encouraged several to go to their very first trial. I have been using VT - Intro as a recruitment method for NADAC.
Another thing I LOVE about Intro, my old dog Ellie, can no long adequately see well enough to run in an indoor arena due to age related vision decline. She can however see well enough outdoors for VT, esp if the sun isn't too bright. She has loved this game for a very long time, and it keeps her fit and still keeps her working. She doesn't usually have the concentration to complete an entire course, except on rare occasion now.
My youngest dog, is not a big fan of tunnels, but the Intro times just make her happy, jumpers she's fine with, Tunnellers.....not so much. She's an odd combo of fierce warrior and afraid of her shadow. Hoping Intro courses and VT's will get her over a lot of her "Sheltie princess" issues.