While this is a step forward, another section of the population are still subject to inequality: those who live together and refuse not to marry. While Lady Hale said she had no difficulty in applying the term "as husband and wife" to persons of the same sex living together in a stable relationship, the state does not offer that perspective on heterosexual couples who reject marriage as an institution.
While a "homosexual couple, as much as a heterosexual couple, share each other's life and make their home together" the assumption is that the latter are married. So there does seem to be a "rational or fair ground for distinguishing the one couple from the other in this context," namely the assumption that marriage is the natural state for couples.
The government has introduced the Civil Partnership Bill to allow gay and lesbian couples to sign an official document at a register office. Yet the assumption that you have to let the state (or church) approve your love and living arrangement persists. That you must register with the state before you have next-of-kin rights is a disgrace. So while we should celebrate the fact that gays can marry, we should remember that basic rights should not be tied to marriage and that inequality remains.