Just received the "live" bulletin from IKEA, 20% discount for SULTAN mattresses and ensemble bases from 15th March to 1st April 2012.
Not sure whether or not it is nation-wide; it should be I guess.
Yet, I only found this offer promoted online on Homebush and Tempe pages:
http://www.ikea.com/au/en/store/homebush/offers
http://www.ikea.com/au/en/store/tempe/offers
EDIT: It's gone on Tempe's page now.
Springvale is on now =)
http://www.ikea.com/au/en/store/springvale
Copied and pasted from Homebush page:
MARCH 15- APRIL 1
Dreams can come true!
Snuggle up and get 20% OFF all SULTAN mattresses and ensemble bases to make sure you get the perfect night’s sleep every night!
Our SULTAN mattresses come with a FREE 25 year guarantee to help you sleep better at night.
Terms and Conditions apply. See in store for details.
They also have three-month exchange guarantee http://www.ikea.com/ms/en_AU/terms/SULTAN_guarantee.html
Beware, even the firmest ikea mattress is too soft for me. As an experiment, I decided to try sitting on their softest one which was on a wooden base; I almost broke my coccyx sitting down.