Two things for me:
Would like to see One Spark run a bit longer next year until Sunday evening or later--who wants to finish up the weekend fun so early? Went downtown on Sunday around 1 pm or so to check things out and grab a bite to eat for lunch, but other than Chamblin's Uptown, everything was pretty much packed up and dead by that time, albeit it was also kind of drizzly out, but still.
I was too lazy to ride my bike and didn't really want to deal with the hassle of 1) looking up the ever changing pseudo-trolley schedule, 2) locating the nearest bus stop and 3) waiting in the sun and/or rain for an hour but I would have loved to have actually been able to hop on a trolley someplace in Riverside to go downtown and back so I ended up driving both days I attended. So, maybe it was really great this year and I just missed out, but next year, I'd like to see more and better trolley service to/from Riverside advertised--short wait times, easy to spot convenient stops, and run it until late at night!
That said, like others have stated, I did really like the convenience of parking at the convention center lot and taking a nearly full Skyway to Hemming Plaza both days I went and loved the event overall and the vibe of downtown when it's full of people and doesn't look so abandoned and neglected.