It would be helpful to have any idea what some of the errors these various problems give as output, even if it is a panic shortly after an attempted boot. Knowing what the problem looks like in those situations where the hardware may not be fully known, would be a great help in making suggestions for possible fixes- and also might help with generalizing with errors that have similar solutions.
A truly odd situation with CQ62-410us compaq/hp laptop which fails due to some kind of apparent BIOS error- pressing escape in order to cause a boot device selection of DVD seems to solve the problem and allow boot to continue. Reference forum post near the end, last 2-3 comments, http://forums.pcbsd.org/archive/index.php/t-13590.html
Some have issues with suspend ob lind close which may be solved by an edit to /boot/loader.conf
#trying to disable suspend on lid close debug.acpi.enable_debug_objects="YES" debug.acpi.disabled="lid"