Had my 07 Brera 6 yrs now and put 60,000 miles on it during that time so it's now up to 102k hopefully I can answer your questions.
1. MPG, I agree with Philjay50 at about 37MPG ... I do a 70 mile round trip M6/M62 daily, don't really take notice of the on board display as it can be wildly inaccurate at times. I just brim it (you can squeeze in 71 litres) and then expect to get between 580 - 620 miles out of that. I just work it on 75 miles per 1/8th on the gauge, it's never really that far out.
2. Competition ... there is no competition. You can't compare a Brera to a mobile hairdressers car.
3. Reliability ... Apart from servicing and wear and usual wear and tear stuff (Clutch/DMF done at 100k ... Crankshaft pulley a few months ago) i've never encountered too many problems ... admittedly springs tend to break (as i've just discovered on my front n/s) but the car is nearly 10yr old and our roads are crap, so that could happen on any vehicle.
4. It's definitely a cruiser, effortless motorway driving, comfortable cabin, plenty under the pedal when necessary, and is there a better looking coupe out there? It's already a future classic in the making.
Oh ... mines the Tractor 2.4jdtm version remapped by Gus @ alfatune, I live in a rural area and believe me some of those big tractors that go past our cottage actually do sound better ... but I doubt if there's any as quick