Yeah one of my friends round the road from where I live had this mod done at the SSDT from JLI. He rode a 05 125 standard for a year, he then got a 06 125 which he thought there was an improvement, but he wanted just wanted a bit more from the bike.
He took it to john and got new jets, new middle box and got the timing advanced. I have to say I thought there was and improvement myself, revs out my better and cleaner. I would say its well worth going for.
Gavin