Packers are terrible. I've never been able to unpack themida or UPX using the available unpackers / scripts on the internet. But some people just throw up the middle finger to Themida and tell it to get fucked, and they win.
The hardest part is actually unpacking, after that you can take a disassembler to it, and be stuck with coding you having no clue of what it means/does. At least that's how disassemblers work for me. xD