It doesn't stray too far from the formula, but it makes the logical progressions you would expect Nintendo to make.
A lot of people are writing off Banjo-Kazooie as a Super Mario 64 clone. Now let's think about this for a bit. Mario 64 was a revolutionary game. It redefined what people expected from a platform game. Banjo-Kazooie follows in the footsteps of Mario 64. It doesn't stray too far from the formula, but it makes the logical progressions you would expect Nintendo to make.
The storyline is fairly typical. Banjo's sister, Tooty, has been kidnapped by the evil witch, Gruntilda. Gruntilda is hoping to use some wacky contraption to steal Tooty's youth. It's up to Banjo and Kazooie, the grumpy bird that lives in his backpack, to venture into Gruntilda's lair and stop the witch before it's too late. Once inside, you'll find an insanely huge overworld and nine levels to contend with. Mario's stars have been replaced by jigsaw puzzle pieces. These "jiggys" are used to open each level. Coins have been replaced by notes. You'll need to have a certain number of notes to proceed throughout the overworld. The red coins have been replaced by birds. Collecting all the birds in a level will give you a jiggy. Each level contains ten jiggys, 100 notes, and five birds. The first thing you'll notice about B-K is its size. The game is much, much bigger than Mario 64. The overworld is huge, and the levels are spread pretty far apart. Usually, the puzzle that opens up a level isn't even near the level's entrance.
The gameplay in Banjo-Kazooie follows Mario, but Banjo and his bird have a lot more moves than Mario ever had. Luckily, there are some great tutorials in the beginning that teach you the basic punching, jumping, and swimming maneuvers. You'll learn the rest (flying, how to use certain items, etc.) as you need them. While Banjo has several different attack moves, I found that his basic roll is usually more than enough to take out all the run-of-the-mill enemies.
Graphically, Banjo-Kazooie takes it to another level. The game maintains the look and feel of Mario 64, but instead of flat, shaded polygons, BK uses a lot of textures. You would think that the amount of texturing and the size of the levels would slow the game down a lot, but it runs nice and smoothly. The camera control has remained the same, but due to BK's many tight, enclosed areas, the camera sometimes fails to show the action from a playable perspective. Expect to miss some things that would normally be incredibly obvious, due to a bad angle. Also, you'll have to control the camera a bit more than you should have to, as it doesn't track perfectly. The sound and music are really well done. The soundtrack is infectious, and the character voices are very cool. All the "speech" is done in a Charlie Brown's teacher sort of way.
If you were a fan of Mario 64, then it's pretty apparent that you're going to like Banjo-Kazooie as well. BK may be a Mario clone, but that isn't exactly a bad thing. In fact, it's a pretty good thing. In a world filled with mediocre N64 games, it's nice to see another truly great game on the system.