It's not truly Banjo-Kazooie, but it's still a great game in its own right.
This game is fun and creative, but it isn't really Banjo-Kazooie. And it's not just the gameplay. The characters look and act far different from their original designs. The "good" graphics cause it to lose charm and nostalgia. Other than Spiral Mountain, the world does not tie into the other games, which also loses nostalgia, as well as an overall sense of familiarity.
On its own, however (which is to say, ignoring the fact that it is part of the Banjo-Kazooie series), the game is addictive and fun, with a focus on creativity and customization, both of which I encourage in games. The Lord of Games is an interesting and engaging new character, and Pikelet and his police force are entertaining, to say the least. As previously mentioned, the old characters don't act the way they used to, but the personalities they're given match the roles they play in the game.
So creating and using the vehicles is fun. The minigames you're supposed to use them in, however, are not. Some are fun, I'll admit, but many of them are frustratingly hard (well, hard to get the TT Trophy for - I'm a perfectionist, so that's always what I shoot for) and not always very well-thought-out. The world, rather than being expansive and fun to explore, is confusing and makes it that much harder to find the place I want to find. The plot isn't very deep or interesting, which kind of bogs down the game.
Overall, the game has ups and downs. Sometimes I really have fun with it, and sometimes I find myself extremely frustrated. The game is worth it if you enjoy the kind of thing it focuses one; otherwise, you'll find it to be a horrible mess. The one thing I can say is that if you're buying it just because it's a Banjo-Kazooie game, consider whether or not you're really going to enjoy it first. It's not like the other games in the series, so don't think you'll like it just because you liked the other games. On the other hand, don't NOT try it just because it's not like the other games. I'd recommend renting it first if you're not sure. Anyway, the bottom line is that it's a great game, but they chose a bad series to put it in (as in, the choice was bad, not the series).