I'll cut straight to it. If you're looking for a 10K to run while enjoying the runDisney experience then hands down, this race is for you. I've done the Disneyland Half 10K twice and this course was far more enjoyable as it was entirely in the park (save for a few moments at the beginning).

Expo: Significantly smaller than WDW, you'll find all the major exhibitors here without the walking! Packet pickup is located underneath the Disneyland Hotel Convention Centre, with gear pick up located in the main expo room (along with the Speaker stage and the general race merchandise). All race bib, pre-ordered commemorative items, park tickets are charity tables are in one place which is extremely convenient, however can become crowded. As per runDisney guidelines, challenge runners need to get their picture taken at pickup so they're able to cross reference at the end of the final event.

Swag: You'll get the technical race shirt for the 10K (Challenge runners will get 3 shirts overall), gear bag and a mini Clif Bar. There's plenty of product samples from painkillers to Clif products to bananas from the exhibitors on the floor.

Course: This weekend's events all start the opposite way from the Disneyland Half & Tinkerbell Half start - heading up Disneyland Drive rather down towards Katella Ave. There's some slight road running before you turn off backstage past the Disneyland Admin buildings, down the side of Disneyland Park (look to your left and you'll see Harbor Blvd!) and coming out around the Tower of Terror before heading back into Disneyland Park. You'll run through the gates and then head backstage to appear in Tomorrowland and BAM! you've hit the 2 mile mark! It's a run through the castle up into Fantasyland, looping around the Matterhorn and through the "Darth Vader" tunnel (it's pretty cool) to Big Thunder Mountain. Once you get through Frontierland you've made it 3 miles, and you've still got California Adventure to go!

Running down Main Street is a completely different experience to running up it as you head out to the supporters lining the space between the two parks. Once inside California Adventure you'll head back towards Hollywood Land and out running a loop up through the tram turnaround points. 4 miles down and you're running behind Cars Land to come out beside Radiator Springs Racers. The colours of the pseudo mountains look amazing when the sun is rising, so definitely take it all in at this point!

After the mile 5 marker you're running around Paradise Bay (all lit up) back up past Grizzly River Run and onto Downtown Disney and to the finish line near the Disneyland Hotel.

NOTE: This course is pre-Star Wars land construction.

Aid Stations: There were three water stops and one medical tent along the course.
There were plenty of portaloos before the corrals and all restrooms are open in the park.

Atmosphere: There was atmospheric sounds being played through the park's speaker system (Star Wars themed of course) and a selected amount of characters were spread throughout the course (some static like R2D2 & BB8). These character stops were incredibly popular and the lines were closed earlier to ensure all runners weren't going to be swept. Additional to the character stops were prop scenes where you could put yourself in the movie - these had shorter lines.
There was also Star Wars themed projections on buildings which added to the overall theming of the event.

Post-race: Disney are great for herding runners through the finish line area. Once you pickup your medal you're encouraged to continue through to photos, medical and food. Food-wise you do get a runner's box full of goodies plus a water (and Powerade if you please).

Since the race area is central to the overall resort area there's no transportation required to get back.

This was a fun and fast course around both parks. I definitely think that this is the best configuration that they can possibly do to keep the kilometres within the property. While they'll change the course once Star Wars land is completed, if they keep the foundation; it will easily be the best course on the runDisney 10K roster!

2016 additional notes: runDisney has changed the process in getting to the corrals at Disneyland and all runners must clear through bag check prior to entering the corrals. Where previously you could just walk straight to the corral, you must now enter through Downtown Disney and loop back down Disneyland Drive.