I have a 57 reg 159 Ti 2.4JTDM (210) and have had it remapped... I had it done at Red Dot Racing about 3 weeks ago and im very happy with it.
In regards to figures, standard it gave 197bhp and 263lb ft torque. After the remap it has 235bhp and 340lb ft torque.
The change is unbelievable, 3rd and 4th gear pull like a train, plus it is alot smoother to drive at low speeds (1st gear). Pick up is quicker and turbo lag is alot less noticable. I would imagine it had knocked a good 1 second off the 0-60 time and possibly even more off the 50-100 figures.
One issue to be aware of is that mine is running on an old ECU (as yours could be too as they are the same age). Red Dot told me that 235hp ish is the most it can take without effecting the reliability. Mine is going in for some work and a service at my local main dealer soon and they are going to update the ECU to the latest version, this will erase the remap but Red Dot will re-install it FOC. With the later ECU they will be able to remap upto 255-265 bhp (not sure on torque but would guess somewhere around 380lb ft).
I get the odd puff of smoke when cold, and sometimes I get a slight hesitation when changing from 3rd to 4th, but this will be cured with the ECU update, and is hardly noticable anyway.
I haven't seen any increase in economy, but then thats not the reason I had it done.
Hope all that helps, you should definatly go for it, it transforms the car! Personally I would get the updated ECU first and run it on a few tanks of premium diesel before the remap to get the best results. (Mine is now noticably smoother on V-Power compared to cheap supermarket stuff).