They have replaced slot of the trail this past winter. There are still some bumpy sections . But can’t beat the tranquility of the wood and the bay for a good ride. You can’t go flat out but you can get a good relaxing ride in. Go early it’s gets crowded at times

This is a pleasant escape from the city, largely running along the creek and through woods, but occasionally popping out and paralleling residential neighborhoods. There are also hiking paths off the trail.
I love that it's a full loop (no backtracking!). It's well-maintained and quite flat, so it would be appropriate for all abilities. The southeasternmost extension (behind brewery and post office) is not as well maintained.
The northwest end of the trail (off Harford Road) is about a block from Lake Montebello, which has bike lanes running around the lake (and, as of May 2020, the roads around the lake are temporarily closed to cars). So Herring Run + Lake Montebello forms a pleasant, no-backtracking, extended loop. Also, as of May 2020, Harford Road is under major reconstruction, so finding the entrance to the trail from the Lake Montebello end is a little tricky (there's a temporary path carved out that's quite rugged and may create accessibility issues for those with limited mobility).

This section is complete. Paved and spacious. Not much elevation but good for a jog with a stroller from one end to the other and back. What’s not to love? Parking ok Crownsville is limited (two larking spots, 3 including a handicap spot) but the Rt3 lot near end of Millersville Rd has plenty of parking.

Made it out to this trail last weekend. While some areas did get a little crowded, was a relaxing and beautiful walk.

Have done this a few times. I enjoy having this much mileage available without having to interact with cars on the road. And nice access to additional trails connect to this. Well maintained and a great trail for base miles if you don’t want elevation gains.

My wife and I just got “real” bikes and for Us it was great. Well kept trails and paved all the way. If in area it’s a must.

New section recently opened. The eventual path will link up with the B&A trail for serious mileage.

I've ridden the south/southeastern section (from Downtown/Federal Hill to Middle Branch Park/Cherry Hill) and the northwestern section (Leakin Park/Gwynns Falls Park, from both ends at I-70/Franklintown and Dickeyville to Leon Day Park/Trailhead 4 on the edge of the park and Baltimore City.
NW section (Leakin/Gwynns Falls Park): this is a gorgeous park, a natural oasis in the city (very wooded and nature-y). There are lots of side paths to explore (including hiking trails) and other amenities. The section to the SW (between Trailheads 3 & 4) is unpaved and there are some trees blocking the trail, but it's easy to lift your bike over them.
Tip: as someone who doesn't like backtracking, you can create a loop between Trailhead 1 (I-70) and the Dickeyville endpoint in the north by going off trail. Some of Forest Park Ave is fast/dangerous and lacks a sidewalk, but you can ride on grass for 2 blocks. This puts you into the charming and idyllic, Mayberry-like historic village of Dickeyville (an 1700s mill town) before re-entering the park.
SE section: There's a small wooded oasis behind the casino/south of football stadium. The portion through Westport is on-road and industrial. The Middle Branch Park section is flat, through a basic city park, but is along the water with pretty good views.

This is a nice, route with plenty of places to stop along the way. Although it looks like it gets busy, others using the trail seemed aware of their surroundings for the most part. I really like the coffee shop in Severna Park. There is an entrance in the back so you don’t need to go around. Coming from the north, the directions are a bit confusing. Better signage would help.