It DOES actually, yes!
More torque at low revs means a more pleasant driving experience, less gearchanges to get where you want and gets to the high revs a lot more quickly.
I'm not in a huge hurry to sell, I've had it sat in the box on my mantlepiece for over 3 months now so a few more weeks isn't going to make much difference!
It's really simple to fit, yes. The ECU in under the passengers footwell. You'll find that there is a piece of the carpet velcro'd down and there is a removable panel under there which houses the ECU.
Take this off, unscrew the ECU and take it out. Take off the top cover (this is all within the space of 5 minutes, by the way) take out the old chip in it's holder and replace with the Squadra.
Refitting is the reverse of removal.
Boxer engines are hardy little buggers, just remember to check the oil levels and not rev them from cold and you'll get plenty of life out of it.
The water pumps are apparently a weak point at about 70k, but mine was fine right up to 96k when I sold it (it was a 1996 P-reg car).
Make sure you get the belts (drive and auxiliary) changed along with the pulleys etc if they've not been done.
It's not as big a job as the Twin Sparks, so costs a lot less (I paid £150, but I was quite lucky). Others quote around the £200 mark, but nowhere near the £350 minimum needed for the Twin Sparks.