Great question! I'm currently using a standard Android tablet (though I've tested it on my phone too). The great thing about EPub Reader Pro is that it syncs across both, so I can switch between devices depending on where I am.
Honestly, the main requirement for me wasn't the hardware—it was the software handling the formatting. Most default readers struggle with .txt script files or compress the formatting too much. This one keeps the indentations and action lines (like my EXT. ABBEY COURTYARD bits) intact, which is a lifesaver.
What hardware are you using for your dev workflow?