Pros:
Root River has got a lot going for it, especially for a course as new as it is.
1) Challenge/Variety - this course is going to appeal to a wide range of skill levels with dual tees on some holes, and 3-4 possible basket placements per hole (which get moved around periodically). The 5 hole wooded section early on in the course has 3 or 4 of the 10 most difficult holes in the area, especially if you're shooting at the long pins. Course is more forgiving and much more wide open from 7 on.
2) Tees/baskets - all concrete tees, fairly new (the course didn't even exist until around 2013) and in good condition. Baskets are all Chainstars in decent condition. Judging from MKE county having replaced baskets with color banded DisCatchers at the other County Parks, this could potentially be coming down the road?
3) Tee signs - the old wooden signs have been replaced with new, more comprehensive signage, with pin location indicators and more accurate hole distances than they used to be. Pay attention to the tee signs - this is often going to be the best indicator you get of "next tee" location.
4) Decent coverage with comfort items - benches at nearly every tee, and a practice basket at the beginning of the course.
5) Natural beauty - I love the heavily wooded section early on - this is my favorite part of the course, but once you get into the open by hole 7, it's going to mostly stay that way, but you're still shooting amongst visually pleasing terrain with a smattering of large, mature trees.
6) "Water Optional" - this, I thought, was a nice touch: Water does not really come into play at all if you don't want it to. Several long tees put water into play where you have to cross either the course's namesake river, or tributary creeks, but the short tees (save for 15, where you could still meathook it into a little creek) keep you away from the water.
Cons:
1) Hole to hole transitions - the course plays alongside a semi-busy parkway, and will force you to cross another relatively busy road (twice, in fact) that cuts perpendicular to the general shape of the course. You'll be crossing roads (much busier than you're probably used to at a DG course) here a lot, and some of the walks between holes can get quite long. Make sure you have a map - the 1-2, 9-10, and 16-17 transitions aren't readily apparent from just following the flow of the course.
2) Trash cans - I've started doing a "water bottle" test (you can call it a beer can test if you wish lol) where I down a drink early on in the course, then see how many holes it takes to find a trash can. I think I was carrying this particular empty water bottle from hole 2 or 3 until I think 8. Course could use more frequent trash receptacles.
3) The early wooded section will lead you to think you're playing an absolute meat grinder of a course through the woods where you need to deploy every shot type & disc you've got, but all of a sudden, you're out in the open after hole 7, and it's more or less wide open from then on out. The overall wooded/open variety is comprehensively decent, but eventually, the optimal strategy of just launching backhand bombs on most holes starts getting monotonous, though you can counter this somewhat by playing some of the longer tees across waterways, and occasional long pins force you into wooded pockets.
4) No parking lot - street parking only. Not the fault of the course designer, but there are parkway roads that hug both sides of the Root River at this point, and though most of the course plays on the north side of the river, holes 1/18 are the only two on the south side of the river, and thus, you'll want to park on the southern parkway road.
Other Thoughts:
Overall, this course is a solid, relatively new addition to the Milwaukee disc golf scene, that when considered as a whole course, does offer a good amount of variety and challenge. Course maintenance is generally pretty good, though I've been advised by the local DG Facebook group to expect maintenance to suffer a bit due to budget cuts related to the COVID-19 crisis.
Root River is a pay to play course, though I think you get good value - a $5 daily entitles you to play at all MKE County Parks courses for the duration of the day (includes Estabook, Brown Deer, and Dretzka), and a $40 annual pass is a damn steal to any area DG player.
Guys with big righty backhand power drives are going to love this course and score well - as a primarily forehand shooting player, I thought there were a lot of holes took away usable forehand (or LHBH) lines by placing tee and basket adjacent to thick woods on the left, so it really forced me to adjust my strategy...I didn't dock points for this - this is my own problem! But, if you can consistently put it 350 to 400' where you want it on an RHBH line, you'll eat this course up. Forehanders and lefties will probably like the wooded section a lot more, as there's much more use for those lines in that part of the course.
Overall, I'm going to stop short of calling Root a destination course that you need to come drive significant miles to play (I'd still put Root clearly behind Dretzka and Brown Deer in the MKE County Parks pecking order), but it's a highly recommended play if you're around the MKE metro area.