The IHT change is just spin
Currently using a Discretionary Will Trust Clause in their wills (which anyone likely to be troubled by Inheritance Tax will have already done), both partners in a couple can each get a £300,000 Inheritance Tax allowance which the government announced last year would rise to £350,000 per partner by 2010. Notice the figures, £300,000 per partner = £600,000 per couple, rising to £350,000 per partner = £700,000 per couple.
This is just this announcing things that they have already announced just in a different way.