The lovely Courtney spent her Sunday the same way I did, and has some thoughts for you. Her commenters have more.
I would note that Courtney may be seeing a British subtext through American eyes here. Rowlings has mined a familiar theme of the minor functionary who is able to make peoples' lives miserable, precisely because of the respect for authority and rules that exists in British culture. This is also an important subtext in private schools, whose quality of leadership matters deeply (and Dumbledore types are rare).
I don't see the same gun control allegory here, either, as casting spells is what wizards naturally do. Preventing this is just one more example of educrats' denial of the students' personhood, though the danger angle adds impact. It's a story about and for teenagers, remember - politics aside, this is the way they tend to see all authority.
I must admit, however, that there were many aspects of the book that brough the back door EU power play in Britain to mind: endless petty regulation, alterations in the justice system, not to mention willful denial of the most obvious external threats.
Anyway, enough politics. Harry Potter & the Order of the Phoenix does have some good scenes, some appealing new characters, and a pacing that returns to its customary form near the end. It could have been great.
Overall, however, I was disappointed by this book, which would have been better if it had been about 150 pages shorter. It took too long to get rolling, often seemed to be foundering in meaningless sub-plots, and had a couple of connectivity glitches that caused me to flip back through its pages in puzzlement. What could have been a platform for the book's 2 most appealing characters to shine was wasted (though they do get one really good scene near the end), and the tenor never quite rises to the intended levels of either comedy or tragedy. I really liked books I-IV, but felt this one fell short of the mark.
It seems to me that Rowling is feeling quite as pressured as her main character these days, and that isn't a good sign. Might I suggest an author-to-author conversation with Joss Whedon (magic & monsters as an allegory for teendom, exposition through action), and J. Michael Straczynski (serious good & evil in a typically light genre, tapping rabid fans to help build the story as well as drive the market, producing to ridiculous deadlines while keeping a vision intact)?