It's a long game but it earns every second.
The technological marvel I'm referring to is the mass of the game. the smallest level in and of itself is probably large enough to fit the first 7 levels of Super Mario 64 in and still have room. This is not so much frustrating as it is exciting. Personally out of all the things with DK64 I must say the levels are what earn the rating.
The bosses are also quite something to gawk at but honestly some can be pushovers. However please not the emphasis on 'some'. The final boss can take forever to beat as can the factory level and galleon level boss. Also some challenges can be frustrating such as trying to find the spider mini-boss in the forest level.
However back to the levels part of the review. Honestly every single last one level is huge, even some that normally are constricted in other cases, are expanded. For example let's take an example like a haunted castle. Most levels would include perhaps the inside (not that big) and the outside (not that big). This level includes: the pathway up, a haunted museum, the castle grounds, the sewage system beneath it, inside a haunted tree, the greenhouse, the top turret and the crypt and that's just one level.
The best part of it all has to be however that the levels are big enough to be revolutionary but small enough to not be frustrating.
But don't get me wrong, lots of things are great with this game too. The enemies rank just fine on a scale of whether to be total rubes or be intelligent monsters. The bosses are also pretty awesome. One of the most unique ones is when you have to send the Kongs cannonballing towards the pop-up carboard cutout of King K. Rool.
If there is a flaw it has to be the (you guessed it) camera controls. The worst part though is that one can tolerate it in Banjo-Kazooie and Super Mario 64. However by 1999 frustrating camera angles should be a thing of the past but it ain't.
Nevertheless Donkey Kong 64 is a great game and deserves more credit than it's given.