Ok, the Sugru has cured, and I've just spent a while playing Mario Kart 7 - to the point that I completely lost track of time!
This is very, very rare for me with most modern-day games, so you can already guess from that how absorbing it is.
Anyhow, I don't want to spoilerise any tracks, because they've all got tons of stuff that'll make you go "Wow!" or "That's neat!", and it's no fun if you've already heard about it from someone else.
So, I'll just summarise some points of note...
1: The controls are great. I had feared that the horrific layout from Mario Kart DS would be back, but it seems that someone this time around noticed that they shouldn't have employed a crustacean to design the control layout, and thus an extra accelerator button has been added in a more comfortable spot (this means that both Y and A act as the accelerator - I use Y, as I find that using A for it is quite painful). I must give kudos for this, because this issue made Mario Kart DS nearly unplayable for me back in the day. The only thing missing here is a menu with which to fully customise the layout to your liking, but for me, the extra accelerator button is good enough - maybe next time?
2: As with Star Fox 64 3D, the 3D effect actually does make a difference to the gameplay, in that it once again allows your natural instincts to work as they're supposed to. This makes driving, dodging, aiming, and just about anything else you do in a Mario Kart game, much more intuitive.
3: Graphically, it's lovely.
As I said a few posts back, I'm not generally one to be impressed by this sort of thing, but Mario Kart 7 looks nice, has anti-aliasing (which some silly people thought that the 3DS couldn't do, even though the DS could), and has a frame-rate of a constant 60fps whether you're in 3D mode or 2D mode (some folks believed that 3D mode only allowed for 30fps, and whilst this is true of earlier 3DS releases, it's clearly not the case here or with other recent games).
4: I haven't seen any reviews mentioning this, so I'll make a note of it here: You CAN use the first-person mode without the gyro controls. Hit up on the d-pad to switch to this mode, and hit down on the d-pad to leave it.
The handling is good, and the tricks (retained from Mario Kart Wii) are now activated by hitting the hop/drift button when in the right places.
Also, the kart customisation is great, though it's not as in-depth as the car-customising in Mega Man Battle & Chase. That said, I already have a kart that handles a lot like my beloved Treble Darkstar from Battle & Chase, so that's a win for me!
My only real gripe with Mario Kart 7 at this point is that Miis aren't available right off the bat - after all, I have some Mega Man ones that I want to play as, since I strongly doubt that Capcom's ever going to make a follow-up to Mega Man Battle & Chase. (Alas.
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One thing about the courses that I will mention is this: The Wuhu Island ones are great. If you're not familiar with Wuhu Island, it's a location from Wii Sports Resort, Wii Fit Plus, and Pilotwings Resort, which has some points discoverable in Wii Sports Resort and Pilotwings Resort which confirm its connection to the Mario universe. It's great to finally drive around it - they've been hinting at it in other games (specifically, Wii Sports Resort and Pilotwings Resort) for years!
All in all, everything is well-presented, everything is fun, and I haven't come across anything irritating. I have to contrast this with Mario Kart DS, with which I noticed the annoying niggles with the controls and over-reliance on drifting and "snaking" right away, and never enjoyed it as much as, say, Mario Kart Wii. It's the best handheld Mario Kart so far, without a shadow of a doubt.
If you like Mario Kart, or just like good, old-fashioned arcade-style design and fun, you will want this. There is nothing else I can say that would do it justice.
Get it now. Off with you. Go.
EDIT: Also, there is one unusual thing that most people probably aren't going to notice: The game, at least in Europe, is not supplied with a full manual - only a quick-start guide (the game itself has a full manual on-board, which you can access from the 3DS' menu). There's some silly line printed on said guide that it's to cut down on the amount of paper used in the packaging, but I would imagine that whilst this is a side-effect, it's probably more likely to be due to the fact that almost nobody reads the manuals for the Mario Kart games anyway, as they're so easy to pick up. Why waste the paper and the money, given that?
EDIT 2: Oh, and the Blooper (ink) weapon is genuinely dangerous, now! (Unlike in Mario Kart DS, where there was a particular spot that you could see through, which gave you a good view of what was coming up.)