PiYo - any thoughts please?

Yes. Piyo is great because I have terrible knees, but also suddenly I have muscles in my arms that I NEVER had before. EVER. I was so shocked, I thought they were some sort of growth or tumour until I realized they were symmetrical and also kind of hot.
I don't know where you're starting from, though- I was starting from close to nothing- I had worked out before with Insanity, which was great but terrible for my knees, and then taking a super long break due to laziness/distraction/life. At this point I do PiYo about 4 times a week and, combined with food changes, have lost 30 pounds (sort of slowly- over the last 7 months). I am currently about 4 pounds away from my first goal, and 16 from my maintenance goal. I recommend it highly, but again, it all depends on what you like to do. I like the fact that there's no jumping, no running, and I'm not really ever out of breath (I do sweat buckets during it, though), and that my muscles are clearly working and getting stronger. Also, it doesn't take all that much time out of my day but I don't feel like I've been cheated in my workout.
I also like how I fit in my skinny jeans. The guy at the store actually said "wow" under his breath, which maybe he says all the time, but it was such an ego boost anyway. Better arms, better legs and butt, better core... I love this.
Wow, this is longer than I meant for it to be. Anyway, I say yes to PiYo.