Definitely worth it... as above, smoother and more responsive... and I think slightly improve mpg - depending how you choose to use the free'd up power!
I fitted mine a while back, and seem to remember blanking off a vacuum pipe... I got a kit from TD5 Alive, and it came with all the bits you need and a good set of instructions.
Best thing - from advice here - get some Plus Gas spray on penetrating fluid... spray a couple of times over the days before you do the job, my manifold bolts came out no problem... you do hear of dramas with them shearing.
I've tried a few mods, and I rekon this was the best value for money.