The test drive last night went great, nothing came loose, no shorts, etc. Being the paranoid person I can be sometimes, I took my garage fire extinguisher with me in case of some horrible battery incident, but it was totally unwarranted
It seemed like the car handled better, although I didn't do anything too aggressive on this drive. The car just seemed flatter and more neutral through corners. I wasn't really expecting to be able to feel any difference from a single weight reduction/shift mod, but I guess the battery is a pretty big one.