Firstly let me say that the new version is a great leap forward and has been fun to use. I did run into a few issues which I thought might be worth pointing out.
In 2.0.0 (official release) when loading samples into Layers 2-6, Spark would only play back the sample loaded into Layer 1, despite the trigger mode setting. This issue was present every time (20+ instances) upon loading Spark in Ableton Live 9.1.1 (Windows 8.1). It actually caused me to uninstall and move to the 2.0.1 beta.
In 2.0.1- when using the "Roller" function on the hardware in conjunction with the trigger pads, a constant triggering latency appears which does not resolve until fx mode is changed. Also, during playback in the DAW sequencer and while editing a sample in Layer 2 (in stacked mode), Layer 2 stopped triggering entirely. Layer 1 kept triggering but was only playing the original default kit sample. I was able to load different (Non-Spark) samples into Layer 1 but it still continued to trigger the default sample from the Spark bank. This has only happened once and resolved when I stopped the sequencer and reloaded the default sample.