No, I don't like it. Our ancestors spent centuries seeking to divorce the monarch from political influence and only partially succeeding. Then this cabinet, with absolutely no sense of political history, think that it's a good idea to invite the Queen to attend cabinet as an observer. Her Maj has an undeniable role in government, from opening parliament to signing off legislation. But, for my lifetime at least, that role has been ostensibly decorative rather than practical. By inviting her to attend cabinet, Cameron and co are messing up fine distinctions and long traditions.
Furthermore, it creates an unwelcome precedent. As far as we know, the present queen has been admirably punctilious in observing the constitutional proprieties (at least until now). But what of her successor? Could we trust him to keep his mouth shut during a cabinet discussion? Could he be relied upon to keep his distance from political decisions?