Personally, Matt Smith is by far my favourite of the post-Baker Doctors, and Moffatt is my favourite 'current run' doctor who writer. It's just such a great return to the style of the Troughton doctor and the Pertwee-era horror. RTD was decent, but relied far too much on trying to make each ending 'the biggest epic yet', which got silly very quickly, and almost always couldn't find a way of resolving them, relying on an ultra-schmalzy deus ex machina (e.g. ruining the awesome 3-parter that reintroduced the Master with a goddawful ass-pull ending).
Moffat's also shown a lot more faith in the audience by raising the intelligence of the show, and trusting that the audience will be smart enough to keep up.
Edit: we don't use the word 'gasoline' in Australia, but it struck me as the obvious term to use in the context. Surely the 'gasoline' thing was deliberately put there to emphasise that the characters are in the US? Standard writing, and they'd do that all the time with the original run (I've watched every single doctor who episode from its 1960 beginnings, aside from the ones that were lost in the BBC fire - and of those, I've even listened to the audiotapes and part-episodes that are left, so I know my DW history
).
It's just standard scriptwriting for any British TV show - if the characters travel to a location that has a local dialect/custom, the writer starts throwing in a constant string of reminders that that's where the characters are, so that it's easier for the audience to follow where the characters go. If you have someone in Thailand, you have them using Thai words every now and then, or you have them wearing a peace of Thai clothing, just so that the audience can be reminded without having to go 'hey we're in Thailand right now, remember?'. It's pretty straight up stuff that you're going to use gasoline if the characters are in US and the chance comes up - same reason why they have the Doctor wearing a Stetson (though that also being to distinguish future doctor from present doctor).
Not to mention, it makes sense given the context (even aside from being a common writing trick that Doctor Who used all the time in the 60s/70s, especially in the early Hartnell 'historicals'). We know that Amy and Rory must have been travelling through the US for some time now. They have flown to the US and travelled by BUS to some middle-of-nowhere place in the desert. Even if they went straight there, they'd have to have been there for a week or so. When you travel, you end up using the terms of the country you're in. Done it lots of times, myself. Especially in an insular place like the US - people tend to insist on you using 'their' word in their country. But even if they don't, it just happens - the signs and the ads everywhere say 'gasoline', the bottle that you're pointing at says gasoline, when you suggest that you use the stuff in the bottle you end up saying 'gasoline', even though you wouldn't use that word at home.
I can appreciate joking about the 'gasoline' thing, but if you're serious then I'm glad the writers know better than to throw out a standard writing technique (use terminology as reminder of location), and to ignore the word the character would actually use in the situation when he's been travelling through the US and is pointing at a bottle with 'gasoline' written on it in big letters, simply because the word happens to come from an intellectually impaired....I mean, the US.
And personally, I don't see how any fan of the early DW, especially the pre-Baker series (Troughton is the obvious comparison to Matt Smith, but I'm referring to the writing styles of the first season of John Pertwee as the Doctor (1968?) as well), could say that Moffatt's writing is less true to the series' original tone than RTD's writing was. I'm not saying that RTD didn't fit the series - he did a great job on a lot of elements, though he always produced his worst writing in the season finales, but the personality of the current Doctor is a much more natural extension than Tennant was (and I'm a fan of Tennant's work, including his non-DW material).