I skate the portion from Dougherty Road to Bollinger canyon regularly. The pavement is in fairly good shape with few road snakes (Cracks). After Bolinger, heading north it turns to concrete with expansion joints and is not the most pleasant ride. North on Norris Canyon road it is back to pavement, but is in need of repaving/resealing as the gravel and debris increases there.

Also south of Dougherty Rd is not bad going to BART. It is really ready for resealing or repaving, but is ridable as of right now.

This trail goes through mostly suburban areas. On a weekend there are lots of bikers, joggers, dog walkers, and kids. This trail passes by lots of residential areas so its well used. North of Pleasant Hill the trail follows a wide creek. In March, there was flowing water with wild flowers, geese and ducks. Through the City of Walnut Creek, the trail passes along the creek, which here is in a giant box culvert. In Alamo and Danville the trail passes behind big homes with a mature Oak Tree canopy. Further south in San Ramon and Dubin the trail follows another creek. San Ramon is home to the 2000 acre office parks. There are also some recreation fields and some houses/appartments as well. The trail is adjacent to two BART stations, and somewhat close to three more. If you live near BART, you can have a car-less day on the trail. If you want to ride it one way start at pleasant hill station, 4 miles from the north end; and finish at Dublin station in the south. North Concord station is about 1.5 miles from the north end. I suggest checking the weather first and riding the same direction as the wind, usually from North to South.
Be sure to get the trail map from East Bay Parks (EBRPD). It is available free at some of the trail kiosks, or search the internet for "EBRPD Iron Horse Trail".
There are two places where I missed the turn. Northbound at Monument blvd in concord, be sure to turn left (west) and cross the creek. There is a gravel path that continues straight, but this is not the trail. the Iron Horse trail is 100% paved, so if you are on a gravel road, you made a wrong turn.
Southbound at Rudgear Road in Walnut Creek, after crossing under I-680, turn right (north) on Danville Blvd for 0.1 miles. I turned left because i was going south and thats South. But its 1 mile until there is a way to get back on the trail.
There is a trail overpass under construction (march 2010) across 11 lane Treat Blvd in Pleasant Hill. This matches an existing overpass across 9 lane Ygnacio Valley Rd in Walnut Creek. Yes this is suburbia, and there are lots of cars. Its nice to see the city and county investing serious money in the trail experience.

"I have ridden this entire trail more than once and frequently ride parts of it. All in all, it's a great resource, but it can be clogged with pedestrians, dog walkers who refuse to keep their dogs close, baby strollers, and more, on nice days. There are also numerous road crossings where you really need to look out for soccer moms driving Himalaya class SUVs (especially in Danville) to avoid being run over.

All this being said, it's still a great place for a ride. I've used it to commute from San Ramon to Walnut Creek often, and it's convenient, well-maintained (in most spots), and a wonderful asset for cyclists, walkers, etc.

You just can't really get up to speed and stay there because of the foot traffic and crazy drivers at crossings."