The more likely solution is for enTourage to optimize the eInk software, which is written by them. enTourage has done some amazing things in the past in speeding various things up by releasing patches. Android, as the operating system, isn't really involved here from what I understand.

You should also go into the Journal Preferences and enable "Quick Draw". This will give a dark black line when writing and when you save or tap "Refresh", the line will be redrawn at the designated thickness and colour (and higher quality). I think this option is on by default though.

In any case, I think if you focus on writing and not on looking at the ink that you may be able to ignore the lag.