True, dwarves will obey burrow designations just fine. That part I'm not concerned about.
However, if you assign all your haulers to a burrow, and then hauling jobs are generated elsewhere outside that burrow, the !!CANCEL SPAM!! lags your fort so badly that you end up turning the burrows off. This is tolerable for short periods of time like sieges, but it means that you can never have a long term burrow set-up and decent FPS at the same time.
Is there a way around this? Or are burrows, though mostly functional, still affected by a glaring bug that effectively renders them sub-optimal?
Yes, dwarfs will still try to haul items outside of their burrows, I'm afraid the coding is too far along to make it worthwhile to change currently.
Only way around this is to assign dwarfs to individual burrows that includes their bed, dining area, food, drink, and materials they need for their jobs; stockpiling materials they need or you want them to use helps. Assigning a team of 'haulers' to collect wood and stone outside of the burrows should take care of most misc hauling jobs, although if you are using the civilian burrows and not individual ones you will be spammed.
Another way to handle this with civilian burrows is to find out what item they are trying to haul and expand a path to said item, or during sieges forbid the item outright. Putting floodgates/hatches preventing access outside of your fortress, calling everyone in and shutting floodgates/hatches will help you determine what they are trying to haul without the danger of sieges. Cancel all mining/woodcutting/building jobs. Also, make sure no stockpiles (refuse, for instance) are outside of the burrows, if they are expand the burrows or delete the stockpile.
For the most part, I harvest all wood every winter and stockpile it inside of my fortress, and all ores are mined from the safety of inside my fortress so I rarely get jobs outside of my civilian burrows.