It was sort of a weird Spike episode. This whole "life debt" thing sorta came out of nowhere (that was hardly the first time he'd been in real peril on this show, or the first time another pony had saved him). Sure, he cried a bit when he told Twilight he had to leave, but it still felt rather slight, especially after the season premier revealed his greatest fear was, in fact, Twilight sending him away. Also, yeah, he's normal,ly much more competent. I mean, he's got a thumb. He should be able to do pretty much any kind of manual (non-bucking) task better than any pony.
Perhaps boredom just messes with his head worse than most.
Still, this episode had a lot of little moments that worked. Like you said, the mane 6 were used very well (this is actually one of the better episodes to have solid, organic reasons for all 6 of them to appear and act the way they do), and there's a bunch of little sight gags that work wonders. Pinkie's bits in particular were excellent, as was the way AJ got Twilight's attention in the library. Plus, I for one am always happy to get more Timberwolves, as they're one of my favorite creatures on the show (and I dug how they were rendered as CGI rather than flash based this time around, made them look that much more unnatural and out-of-place compared to the others). So a funny episode, if not a great canon one.