What is the benefits to fit the above to a A Series motor?

Who has done it and what was your gains and experience?

so you can dial in the cam timing and make it puuuurfect..

or... if you want to advance or retard the cam timing to move the power band, or for boosted applications..

So it will enable you to adjust to power curve slightly, will this mean if you run a big duration cam that you could sacrifice some top end performance for midrange power.

yes that's definitely doable, the only thing you have to be mindful of is the valve clearance when you're making those adjustments

actually that sounds stupid now that I wrote it since the cam is doing the valve clearance *slaps own head

From what I have learned on the VW site, you can make small adjustments to where you want the power band.

My personal opinion, on the A series, I think it is a hell of allot of work to make ajustments. You will probably need to remove the radiator and struggle to see the cam sprocket clearly enough to make precise ajustments.
But hey, that's just me.

i dont think it would be worth it for a single cam with the gear under a timing chain cover low on the engine. twin cam engines or even sohc engines with tunable ecu they are great.

Ecu will be tunable, adjusting it will be the tuners issue.

From what I could gather from the answers, the only gain with it will be manipulating the power curves.

Anybody else with views regarding pros and cons. Can't only be me interested in learning more regarding vernier pulleys on a A series motor.

As far as I have seen, there isn't allot of people here using it. So I doubt it is worth the trouble.