I must admit that I'm in two minds about this apology. On the one hand, I have always admired Turing, and think that the way he (and, it is important to remember, many other homosexuals) were treated at the time was appalling. An apology, although largely symbolic, is welcome and overdue.
On the other hand, there is a cult of hero worship surrounding Turing. In particular, he is given undue credit for the creation of the modern computer, with the popular press largely assuming that he did it single handed. This is further perpetuated by many of the team that worked on the Manchester Baby (one of the early computers), although vigorously contested by their equivalents from Cambridge EDSAC team (arguably the first genuinely useful computer), spearheaded by the indefatigable and eloquent Professor Sir Maurice Wilkes (I am of course biased here; my father worked on EDSAC 2 under Prof Wilkes).
While it is certain that Turing's work at Bletchley made a huge difference to the war effort, had he been working alone it would have been a very different story. Like the development of the computer, the work at Bletchley relied on a talented and dedicated team of mathematicians, engineers, administrators and the like backing up people like Turing. Often forgotten (even by crypto geeks) are those outside Bletchley such as the Y service who collected the signals, and a number of incredibly brave soldiers, sailors and airmen who retrieved the key material of captured Enigma machines, often at the cost of their lives.
If apologies are on offer, perhaps the PM should also consider the Polish cryptanalysts, led by Marian Rejewski, who gave us a major head start and were subsequently treated nearly as poorly as Turing (contrary to the plot of Robert Harris's fictional "Enigma", there was no Polish traitor at Bletchley; there were hardly any Poles there at all).
However, if you really want to acknowledge the contribution Turing and his associates made, there is no better way than donating money to the sadly neglected Bletchley Park museum (notably lacking any significant Government funding, but fortunately supported recently by PGP and IBM, all credit to them). A gift of £25 at http://www.pgp.com/stationx/resources.html will get you a rather classy T shirt, and if your company is looking for a worthy cause, Bletchley deserves serious consideration.
Preserving Bletchley for future generations is a far better tribute to Turing than any apology.