Any recommendations from actual users ?
The files are non-DRM pdb books that I have on old Toshiba e830 PocketPC.
I am specially interested in software that can handles non English encoding well (Latin2 or Win1252)
I use eReader for my old PDBs on my iPhone as it's the 'official' reader put out by the same company that put out the original readers on Palm and Pocket PC devices. It works quite well for HVGA devices and is acceptable (though the text is a bit pixelated) on an iPhone 4, but as they don't have a dedicated iPad version, I would avoid using it on that device.
edit: Looks like I spoke too soon - eReader just released an update today that includes a native iPad client, though it looks like we're still waiting on a retina display version.
You can use Calibre on your desktop to convert your PDB books to ePub. See here for the list of supported formats in Calibre.