I got mine this week as well. My mind isn't quite made up, though. I've always like the Bias FX interface, but the Spark's is like Bias-lite. You have three slots for stomps before the amp and three after, but they're dedicated to the stomp-type (e.g., #1 is a gate, #2 is compression, #3 is drive). Post amp you get a Mod slot, Delay slot, then Reverb. With the regular Bias FX, you can make a chain a mile long, change the order, split it or stack effects.
Tone wise, it's OK. Most of the amps sound alike to me. If I can get four rigs put together that I actually like, I'll keep it. The play along utility is pretty cool. It searches for Youtube videos and shows you the chord progression in real time. If you pick a tune that hasn't been analyzed, it will play it once and analyze it then.
It's heresy, I know, but I was kind of hoping to use this for practice and selling my Kemper, which I basically just use for practice. I don't gig or record and I don't need to model. If Kemper could make a similar, simpler device, I think they'd sell a million. Image a self-contained unit like the Spark with a speaker, bluetooth and the sound engine of the Kemper. Load and tweak profiles, but no modeling. Maybe someday.