I just heard the end of Any Questions on radio 4 and one caller struck me as interesting.
She pointed out that under the normal tax system a single earner on £60,000 would have a large proportion of their income taxed at the higher rate, 40% tax band. Whilst two earners both on £30,000 (and therefore jointly earning £60,000) would both be taxed at the standard 20% rate of tax.
Havn't heard any Mumsnet users complaining about that...