Whilst you're mulling, have a look at this:
ECU Remapping | ECU Tuning - Quantum Tuning Ltd
I didn't fancy spending £350-£500 on a remap, but my 2.2 engine exhibited the faults that have been pointed out on this forum: low-speed hesitancy and a narrow power band.
I found a London distributor who applied the Quantum Tuning remap to my ECU. The engine was transformed. The car pulls away cleanly from very low RPM and accelerates to the red line with no dips in power. Beautiful. I paid £200.
If you are looking for performance benefits, get the remap. If mileage is your main concern, don't bother. Your mileage will be better, not worse, but not enough to spend £200 on the modification.
The remap is guaranteed. If you don't like it, they restore the original software and refund your money. And, they will come to your home for an extra fee. There is no rolling road, no performance printout, but you can feel the difference when you drive the car.
I am really happy with the results. As far as stress on the motor/gearbox goes, you control that with your right foot.