We didn't really have any major hassles with our contract. Everything in the contract was explained, maybe not in minute detail, but good enough for us. We could actually understand it too. Can't say there were any real 'gotchas.'
Regarding damages for building delays, M will pay us $250 per week if more than 9 months elapses from the start of construction, in our case defined as when the portaloo was dropped off at the block. I think the amount of time allowed for construction varies depending on the house being built though.
We have made variations since construction has started, this was allowed up until the time that materials are ordered and tradesmen are booked for that particular item. As an example we cancelled the paving in the outdoor room a few weeks ago. The adjustment to the price will be reflected in our final payment.