Well I'm only starting Grade 4
I'm going to take all the exams in order simply because I think it's a great structure for learning technique etc. Learning the scales, pieces (and the relevant technical studies) is a great ladder for the whole skill and I'm hoping it gives me a rounded base to work on.
I'm also in no hurry

Yes, I want Grade 5 so I can join my local orchestra (like Jojo) but it looks like that might have to wait until next year. I'm just going to toddle along
trying to keep it all fun (but yes, my long term plan is Grade 8 and a Diploma MWHARRRR HARRRR HARRRR

)
I'm going to take Grade 4 in the Autumn which gives me plenty time to learn all the new scales and arpeggios (my weakest point I think). Right now I'm working on improving my vibrato, which is quite secure now but just a bit slow, securing harmonics and shifting positions. All such fun!!
I LOVE the Grade 4 pieces - they're my favourite so far out of everything I've played and I'm champing at the bit to get on with them. I love the English Dance and I think all the 'B' list pieces are just lovely although my favourite is the Waltz. I haven't really looked at the 'C' pieces but I like the last one.. and Slow Fox is good.
HOWEVER, my teacher has banned me from the new Grade 4 list because we both reckon I'll be heartily sick of the pieces by Autumn!!! So right now I'm working on some harder Mazas duets (lots of double-stopping and position changes.. oh and harmonics (my favourite)), Meditation from Thais, Kinsey studies and the old Grade 4 pieces from the last session (which I'll learn to play with the cd accompaniment). And scales etc.
It's all great fun but I have a major exhibition coming up in June so for the next two months I fear poor Martha is going to be a bit neglected while I fling paint around. Then, as long as I'm not snowed with commissions (!) I will have all summer to play to my heart's content.
Well, that's the plan.....