Ok, maybe I will go for the patches.
But before I need to know one thing: I have just bought my M92 from ereader and it has firmware 1.8.1 20121113.
According to the first message of this thread by booxtor, the latest firmware available at ereader is 1.8 20121113.
The fact that I have 1.8.1 instead of 1.8 means that my firmware is in some way already patched? Do I need to install both patches, only the last or none at all?