So far, I think the writing and the casting has been brilliant. Yes, of course there are inconsistencies, improbabilities and plotholes, but this is Doctor Who and it sort of goes with the territory. But what I especially like about this series is how the episodes all interconnect, how there seems to be a real season arc forming and it's not just seemingly random visits to here, there and everywhere (as well as everywhen) as too many stories in the David Tennant-era seemed to me (but then, that could just be me, as even though I did watch most episodes, I didn't watch each and every one, and I gave up on the ones with Martha Jones in entirely pretty early on...).
With regards to the new companion, Amy, I think she's smart, sassy, and surprisingly empathic and insightful when The Doctor needs reining in (viz. The Beast Below). I enjoy watching the sort of relationship that's developed between her and her Doctor, though I don't ship them as I'm old school and I tend not to ship my Doctors with anyone, except in the case of Nine/Rose. Afterwards, this carried over, for a brief time and sort of reluctantly, into Ten/Rose, but only because the pairing had become canon by then. Boy, was I happy when he hooked up with Donna and she became his best friend. To be honest, emotionally speaking his losing Donna to oblivion affected me more than his losing Rose to a parallel universe earlier on. Anyway, for this reason I was enormously upset by the ending of last week's episode, but luckily The Vampires of Venice has brought resolution to the 'Amy fancies The Doctor'-scenario, and I needn't think about it again. Hopefully.
And The Doctor? I adore him. Energetic, running all over the place like his last three regenerations, quirky like all of them, an irascible, kind, friendly and dangerous genius and a madman with a box who, although he looks human, always remains an alien and an outsider. Matt Smith's portrayal of him fits my idea of The Doctor to a tee, and I love him for it.
Also, I can't blame Amy for her recent lapse of decorum too much, because he is quite cute, really.