I'm definitely no expert with electronics (or anything else), but it really bugs me that you'd never be able to jump start your car if you've got some of these new devices on them. I guess I can handle the idea of having to disconnect the battery before charging it but I'd hate to be left stranded away from home somewhere there wasn't a readily available replacement battery. I guess I might chance getting a jump in such a circumstance.
Years ago I'd known several guys that kept replacement MSD boxes with them (just in case).