Several points - mostly being missed
There is an imbalance in the treaty obligations. This is an outrage. The UK politician who agreed and signed it (the whole cabinet, given their doctrine of collective responsibility) should be castigated, and the UK should take the opportunity of US non-ratification to throw it out and start again. Unless the status quo ante was even worse, perhaps...
This imbalance does not affect the McKinnon case, since he has admitted to hacking the machines (even if his hacking simply amounted to walking through an open door).
The Law Lords' job WAS to assess whether the extradition request was in accordance with UK law - but UK law includes the Human Rights Act, and so those issues OUGHT to have been considered. Whether they were given appropriate weight I don't know - I have not read the judgement.
The punishment should fit the crime. In this case, the proposed punishment is massively excessive - even if you believe the US Federal prosecuting authority's claims that he was malicious and political, rather than a mostly harmless UFO nut.
The behaviour of the Federal authorities was abusive - if indeed they threatened him with a hugely unreasonable sentence in order to induce him to accept a somewhat less excessive (but still excessive) sentence in the US.
Imprisonment in the US system may in itself be a violation of a prisoner's human rights (or even cruel and unusual punishment, in the civilised world), due to the lack of protection from rape, assault and brutalisation from other prisoners and sometimes staff. This should be a consideration. Convicts are sent to prison AS a punishment, not FOR a punishment, if you get the distinction.
McKinnon really should be prosecuted and, if convicted and sentenced, serve his time, in the UK, where he lives and where he was when he is alleged to have committed the offence.
The hacking was ridiculously easy - the machines should have at least been password protected. This does not excuse McKinnon, but it should be a mitigating factor.
The prosecution in the US may simply be a way to distract attention from the woeful security in place, or a way to demonstrate toughness on terror. McKinnon should not be sacrificed for political expediency, and the security lessons should not be lost.
That's probably enough points for now.