Let me start by saying this is one of the easiest gaming related 25 bucks I've ever spent, and while it's hard to find flaws in DLC like this that offers 48 (!) extra maps and new characters for a relatively tiny amount of money, most of these enhanced courses usually are pretty lacklustre. If you compare the original Mario Kart 8 maps to what they've put out for this expansion, it's noticeably less detailed and at times some of these maps from older games don't really fit with the MK8 mechanics. I remember a Digital Foundry video about this from a year or two ago, and I thought they made some great points.
All in all great value, but it's a classic case of quantity over quality, but in this case the quantity is so mindbogglingly much that you'd almost forget about quality.