Pros:
-Solid infrastructure: baskets (Mach X), tee signs, and concrete pads are in fantastic shape.
-Good beginner course. The majority of holes are short (putter or mid for an average arm), and the layout uses obstacles well. Provides just the right level of challenge for a new player. There are a few things that keep this from being a great beginner course, which I will get to in the Cons.
-Still fun for experienced players. This is certainly not a heavily wooded course, but the trees that are available are well used to make you shape a shot. The course flows logically. The park has some hills that are just steep enough to create roll away chances on missed downhill putts. It is a very scoreable course for experienced players, but is still fun regardless of skill level.
-Located in a very nice multiuse park. Picnic area with charcoal grills, public restrooms, playgrounds, etc. Easy place to take the whole family to.
Cons:
-Danger of hitting other people. This is by far the biggest detriment. Even on a cold/windy/snowy Saturday morning, the jogging trail was still heavily used. In the warmer months you are going to be competing with people on the ball fields and picnic areas, too. This is a good problem to have, since the alternative would be to just not have a disc golf course in the park. But still…you will want to pick your time of day carefully if expecting to get a full round in rather than skip holes.
-Only 12 holes. While fun, fewer holes combined with a relatively short layout makes it not really feel like a full round of golf. I would be dissatisfied if this was my home course and played it regularly. But for a once in a while course it's fine.
-The few longer holes feel forced and out of character. Hole #11 in particular seems like a really bad idea. Clearly this course is aimed at families and beginners, so why try to squeeze a 360' hole into a corridor between houses and a busy jogging trail? We probably shouldn't encourage newbies to grip it and rip it in a spot where a griplock can easily go over a fence and hit a kid playing in their backyard.
Other Thoughts:
We've all seen this type of course before. The well maintained, family friendly, neighborhood park that happens to have a disc golf course in it. Disc golf is the afterthought, but hey, it's nice to at least be thought of at all. And as far as that type of course goes Mills Park is actually pretty good. Nice layout, nice pads and baskets, good place to have a putter only round. Just keep in mind that you will have competition for the space from other park users, and that it isn't really a "serious" type of course, and you will still have a fun time. I would come back and play again but won't go out of my way to do so.