I love the shred - well all JM stuff really, but Pinot is right, you need to be REALLY careful and tight on form.
My advice is to aim for top notch form, rather than high repetitions early on. Once you have the form and are sure you aren't doing yourself a damage, you can start to rev things up a bit.
Also, checkout some of the individual exercises/positions on y
YouTube etc and work on getting them bang on before you try adding in weights, speed or repetitions. Things like, arm/shoulder positions in push ups and weights, knee, hip and ankle positions in squats and lunges. Knees can easily get damaged if you don't heed JM's warning to never bring your knee over your toes.
I know quite a few people who have had nasty injuries through doing the shred, so it really does pay to be extra careful, but if you work your way into it and always put form first it's well worth doing.
I did the shred last year and lost ridiculous numbers of inches. I found my weight didn't start shifting much until I was nearly finished with level 3 the first time round, but then it came off nicely when I restarted doing all the advanced moves with bigger weights. What I did lose was plenty of inches, right from the word go.
My waist went from 34" to 29", my hips from 42" to 39" and my ribcage from 34" to 32", plus I lost a couple of inches of each thigh, an each off each calf and plenty more across my body.
After I'd been through it twice (first time beginner, second time advanced) I bought Banish Fat Boost Metabolism and started selecting circuits of that to add onto the shred. I did the whole of BFBM at weekends when I had more time, but loved doing the kickboxing and abs circuits daily as they really toned my backside and tightened my abs.
Unfortunately for me I have an illness that has relapses and I have been in relapse for most of this year so far. I have managed 4-6 week windows of restarting the old JM torture and each time the muscle tone does come back surprisingly quickly, but I am a long way of being as fit as I was last Autumn.
I'm really looking forward to getting back into it when I am feeling better.