The good commercial packers will have anti-debugging and anti-disassembling routines in them. The only problem is there's unpackers for most packers out there...

There was a real good packer out there which there wasnt an unpacker for... But I cannot remember the name. But it was $150 :/ ... And there was no crack for the program... Because they used their own packer on their own program, lol. :|