How fast is your MicroSD card?
The lag time on mine was so bad they were unusable and everything (even Firefox) kept crashing. Then I was told to replace the MicroSD cards with the fastest ones I could find. I think the write times are in the 85-90Mb/s range. Anyway, they now fully boot in under a minute and Firefox works flawlessly. Only issue left is Chromium doesn't work so I'm left with one browser (which so far hasn't been an issue).
I'm now using two at my office as browser workstations for when sales people come in without their laptop and need to work. Like them enough I have since picked up a third so I can evaluating what other tasks in my business can be moved off of Windows.