Scoobynet is your best bet for advice on that one. You might even recognise some people over there.
Just to contrast what Zugara has said;
I found my scoob was actually no worse than my Zed is around town (mid to low 20's mpg - I did manage to get that down to a single digit once on track though ). That said, mine very much wasn't brand new. If you're looking at Hawk Eyes, that shouldn't be an issue for you either (it not being brand new, rather than the mpg )
I've not heard of fuel buggering up the ECU, but low RON fuel will munch the engine fairly efficiently unless mapped for it. It'll suffer from knock considerably more than a Zed would on low RON fuel, for example.
The power delivery is quite raw (slightly more refined in a New Age than in the classics) and it's certainly not a GT car. It feels painfully slow until the turbo spools up and you get a big shove in the back as it comes alive. It needs more working of the gearbox for it to shift but it does just stick to the road. The Hawks are quite heavy compared to earlier Imprezas too. It's a completely different car to the Zed so I'd definitely recommend test driving one before making your mind up on them.
Can't offer any insight into the others though as I've never had the pleasure, the only thing that leaps out is that the Elise would appear to be somewhat... less practical than the others you mention.