Depends on your daily drive. If it is a boring, traffic infested episode of dullness, you might as well get a sensible car to do it in, and keep the GT for weekends. If you are ragging it to work on good roads, then it would be a good choice.
For my commute, the diesel 159 is the best choice, unless I am staying at work late, and then the GT drive home is a lot of fun.
I don't find economy that bad - 340 miles on a tank pretty reliably, unless I really thrash it.
If you want to upset the M3 driving neighbour, can I recommend a Wizard exhaust. Makes it sound like a Ferrari.