My impala SS ran better with premium but I used regular most of the time. I find the price of premium in the city crazy, I could usually find it cheaper in the country. In the states I'd always fill up with 93 and have a fun week or two. Costco usually has a good price for premium if you didn't mind the lines.
I'll try some premium in the Journey sometime once it is broken in and see if I can feel the difference.
Anyway, liking the journey so far. I'm still playing with the auto-stick to see if I can "manually" kick up the performance when I feel like it.