Hi Floydy,
Glad you had a good first flight, and yes GA is a little more relaxed than flying commercially - although it can be a bit more hassle at larger airports.
From the weather conditions you describe, I can imagine that it was a bit lively in a 152, and if there was a bit of haze and an the visual horizon isn't too distinct this can add to the brain's confusion and feed motion sickness.
I think we've all felt queasy at some point in a light aircraft - I wouldn't write yourself off just because of one flight, see how you go after another one or two maybe earlier in the day before the ground has a chance to heat up and generate thermal activity and the bumpy ride.
(someone actually in Australia may be better placed to comment on weather patterns at this time of year and when the ride may be best - August and September are the only months I haven't spent time in Sydney so I'm not sure exactly what its like).
Paul.