Registration effectively means tax returns and payments every 2 months instead of annually, with a commiserate increase in time spent dealing with receipts, accounting fees, and likelyhood of an IRD audit.

At the moment receipts go into one of a few, on which I claim back various % of the total (7.5% of house related expenses, 25% of car related expenses, 50% of computer related expenses, etc). I don't need to track GST separately.

And as a private contractor, it may not be as easy for me to pass on all those overheads as for say a retailer. It's not existing clients that (currently) are a concern so much as pricing myself for new clients.

But basically, the less I have to do with the bureaucracy, the happier my life is :)

Yes, you can claim it back, but you have to pay it first - which is a cashflow issue.