I rode this trail roundtrip from Rockdale to Peru (61 miles) over two weekdays in late June, 2011 and pretty much had the trail to myself. You can park your car overnight at the Brandon Road trailhead. The trail is about 70% shaded so it’s comfortable on a hot day. The eastern part of the trail is much better maintained than the western segment. I saw workers applying new crushed limestone for a very smooth ride on part of the eastern segment.

Directly across from the entrance to Buffalo Rock State Park there’s a gate and a sign that the trail is closed west of that point. I kept going and found a long stretch to Utica that has not been maintained in awhile - a bumpy ride on my Raleigh hybrid. A mountain bike would have been better here. From Utica west, the trail was much better.

The worst segment of the trail starts just west of Marseilles. There, the canal and the trail are at the same level in a number of areas so there are many wet, muddy spots. I could get through but mud splattered the bike (and rider). I don’t think this would be at all passable during spring rains. The trail needs to be raised here. On the way back, I took Dee Bennett Road (which was not busy Friday morning) from Utica to the state park entrance where I rejoined the trail.

There are a lot of old locks and dams, some restored buildings and several working aqueducts (where the canal was carried over a river) which make for an interesting ride. The state publishes an excellent map, “I&M Canal Passage”, which details the entire route.

My pals & I set off from Romeoville for the 78-mile ride to Oglesby, IL along the I&M Canal trail. With the exception of ~4 miles in Joliet & ~5 miles after Buffalo Rock, bikers are on a nice path that allows for 15mph+ touring speeds along a nice, scenic trail. Those previously mentioned 9 miles require road riding; the first where there is no trail, the second where the trail is closed while they resolve a conflict with a nearby shooting range.
There are a few stretches (notably west of Marseilles) that could use a little TLC. They are muddy & unkept & ride like double-track mtn biking trails vs touring trails. They WERE navigable, but deserve a little upkeep in order to properly complete what is otherwise a splendid trail.
I would be remiss if I didn't mention the delightful "Garzanelli's Supper Club" in Oglesby, IL. It was a perfect spot for 3 tired soldiers (after the 1st day's 78-mile pedal) to refuel for the run home.

A great path for taking parts of it or touring and riding the entire length. It’s packed gravel and can be ridden with a road bike and skinny tires.

There are several towns along the way, and motels and campgrounds, as well as having camping available along the canal. It roughly follows the Illinois River as well, so there’s several state parks along the way.

It varies between open fields and sunny and very shaded areas where you’re under trees. There are mile-markers and posts explaining the history and heritage of the canal. The path is also part of the GIT – the Grand Illinois Trail – and you can ride about 15-20 miles on highways to the Hennepin Canal Trail. Effectively, the Illinois and Michigan Canal Path and the Hennepin Canal Trail allow you to ride a good deal across the width of the state of Illinois.

"This was an enjoyable trail to ride. It's your normal crushed stone being at least 85% shaded. You pretty much follow the canal which isn't always visible. There's sections where you ride only 3 or 4 feet away, so be careful riding with kids. There's enough towns along the way to stop for a picnic or pick up something in the town. In Marseilles there's a nice Burger King. With very few roads to cross and very light traffic of the ones you do cross make it an idea trail for kids to ride on. If you start in La Salle you have to come off Rte. 351 north of the Illinois River. The bridge crossing the Illinois River is closed for construction."