Is it a good deal: Yes, but only if you don't buy toasters (ie Spend them on flights).
Here is what it costs and how much value you'll get + how many Krisflyer miles it's possible to obtain.
So buying anything over 72,000 points will mean a cost of 1.95c per point.
Anything in international business will almost always be cheaper but there are definitely some economy class flights that can be much cheaper using points.
Some great bargains I've got using points...
Domestic China - 10,000 points + $12 taxes for flights under 600miles (cash ticket was A$430) so ~4c per point value.
SilkAir flights departing Singapore - 14,000 points + ~$30 taxes (done this to Cambodia and Indonesia) when the cheapest cash tickets were $300 oneway. ~1.92c per point (sure not best value but a points ticket is fully flexible).
A few others on Virgin to the Pacific islands have also been good value ~3-4c per point.
Transferring to Krisflyer is also great value and on star alliance partners you can obtain great bargains as well.
Singapore Airlines Business Class from Singapore to NZ... was 96,100 VA miles (converted amount) + $50 taxes for a ticket that would have cost $6000. ~6c per points value.
European Flights on Austrian. Cash ticket in Economy was $1450 but only 27,125 VA points + $50 taxes (converted amount) ~5c per points value.