Pros:
"The Riff" is a park course with some creative design elements that generally take good advantage of the available land to provide a solid, if unspectacular playing experience. Beginning players can experience both long, open holes and wooded, technical holes without being penalized too harshly for missed shots. Holes #1-5 play around a playground in an area with mature trees. Holes #6-12 play in the woods. Holes #13-18 play in an open area with very few trees. Elevation comes into play on a short, blind uphill hole (#9) and a basket on the sloping summit of a sledding hill (#16).
Each tee consists of a single concrete pad, all of which are decent-sized and in good repair, and hole diagram tee sign, most of which are readable, accurate, and in good repair. Holes play to older, occasionally rough-looking baskets, but none are actively damaged, and the catching ability is still pretty good.
Underbrush is managed quite well, and it's rare that a throw from the rough will result in a sting or scratch.
Cons:
The routing is probably the biggest gripe here, as it can be confusing for a first-time player, and remains obnoxious for veterans. The course often seems shoehorned in amongst other park activities and features a couple of long walks, most notably between #5 and #6 where golfers have to traverse the entire length of the park, cutting across a road and two busy parking lots. Starting play at #6 and ending at #5 alleviates some of this pain (see other thoughts), but you're going to have to walk regardless if you want to play all 18. This type of open-ended U-shaped (or C-shaped in the case of Indian Riffle) routing works for smaller parks, but not for the massive park complex here.
The difficulty level is excellent for beginners and rec players, but can get tiresome in a hurry for higher levels looking for a challenge. Most players can avoid the mature trees with ease on the wooded holes, and the open holes leave a great deal of room for error.
Indian Riffle's other big problem is the mud. After any precipitation, most greens turn into a sludgy mudpit that gets discs and shoes nasty in a hurry. This is especially noticeable in the spring with the combination of rain and snow melt. Apart from most greens, other troublesome mud areas include the walk to #8, the #9 tee, and the #12 tee. If it's been wet at all, you'll want to bring extra shoes to play in.
EDIT 5/12/15: Park maintenance has removed a number of trees from the area that houses holes 1-5, possibly due to the Emerald Ash Borer. Regardless of why, the removal has made these holes significantly less challenging/fun/interesting. As a result, I've lowered my score from 3.0 to 2.5.
Other Thoughts:
On the whole, the park is very well-maintained, but fairly high-use. Even on days where there may not be many fellow golfers, it's not uncommon to wait on tee pads for other park users. I never played the original design, but apparently holes #5, 17, & 18 have been modified in recent years to address some safety concerns associated with the high concentration of other patrons. You'll always want to be alert when throwing, especially on the playground and open holes.
PROTIPS: Many of the locals (myself included) play the routing 6-18, 1-5. It doesn't make for a spectacular finish golf-wise, but it leaves the long walk to the other side of the park for post-round, rather than mid-round. As you approach the Kettering Rec Center at the end of Glengarry, take a right into the parking lot and park at the furthest point from the building by the hole 6 tee.
In an effort to make #17 more interesting, many golfers will throw from the top of the hill to the pin below rather than using the concrete tee pad at the foot of the hill. As you face the #16 basket with your back to the #16 tee, look beyond and slightly left for a worn-out patch of earth. This is the guerrilla alt #17 tee. Take extra care in watching for other park patrons when executing this tee shot.