Ive just completed a dissertation on the nineteenth-century governess in Britain and must say that it's led me to be strongly critical about common ideas about the theme of social class in 'Jane Eyre'. .
Jane does indeed assert that she is Rochester's intellectual equal despite her poverty. However, I don't believe that such an assertion was against the middle-class social norms of the period. Ill-treatment of the governess had become a topic for wide debate amongst the educated classes during the 1840s, with many authors pleading for her status as a lady to be more respected by employers. No contemporary author I've ever come access argued that the governess was not a lady, despite being well aware of the poverty in which most of them lived. They were regarded as genteel, well bred but unfortunate women, and many writers advocated that they should be given the same social standing of their employers. (See K. Hughes, "The Victorian Governess" if you're interested) From reading Charlotte Bronte's correspondance whilst working as a governess to the White and Sidewick families in the early 1840s, it is clear that she felt exactly the same way. She hated any task or treatment which implied similarities between her position and that of a servant. .
Therefore, when Jane Eyre declares her equality with Rochester, she is not making a stance that the poor are equal with the rich, but is distancing herself from the lower orders by saying that her education and breeding place her on par with any other middle-class women. Such views would not be regarded as radical in any way in 1847 when the novel was first published. Bronte's essential conservatism on the class issue can in fact be seen from Jane's affectionate but patronising descriptions of the pupils she taught at the village school later in the novel. These were lower class girls who would never reach the governess's gentility, and so were not given equality with characters such as Jane and Rochester.