Just thought I'd update my own thread. The Lenovo IdeaPad S2109 will charge using the little Kindle charger, but it heats up quite a bit (the charger, I mean, not the Kindle). And the experience I have using a 5V charger with slightly higher amperage (1 amp as opposed to 0.8 amps) is that the IdeaPad gets hot, so apparently something is "odd" about the way the Lenovo gets charged through the micro USB port, and it's not just the amperage of the charger. Time for an engineer to weigh in, I guess?
The regular charger puts out 5V at 2.5 amps, or way more than either of the USB wall chargers I used.