I am sorry that I come to this discussion rather late and I hope that I don't digress too much but consider the following:
The posts seem to concentrate a great deal on safety and so they should. Having read everything through quickly I may have missed it but I don't think anybody has mentioned 'rebounding locks'. Of course these are not universal in hammerguns but I would guess that 90% of breech loader h'guns in use today are so equipped.
For those not technically familiar with rebounding locks, they are usually credited with allowing the gun to be opened, and closed when reloaded, without lifting the hammers to half cock.
This is of course true but the system also acts like an intercepting sear on the tumbler when the trigger sear is disengaged with the main bent without the trigger being pulled.
This exact 'double bent' system can be seen on many modern O/U's and is usually heralded as a worthwhile safety feature.
It must be admitted that I have seen more than a couple of h'guns where the rebounding is not properly functioning.
Either the hammer comes to rest against the striker (in the rebounding position), far forward enough to cause the striker to protrude from the breech face: extremely dangerous and arguably not functioning at all as it should be;
Or the hammer takes up the correct clearance from the striker but can be pushed through the rebounding position to push the striker forward (without pulling the trigger). This is obviously a failure in the 'intercepting sear' part of its operation.
The former usually indicates wear in either the tail of the 'captive' leg of the mainspring where it connects with the tumbler toe and bounces it back to its rebounding position or the tumbler toe itself.
The latter usually indicates that the 'half cock' bent is worn and does not 'capture' the sear nose correctly.
I would argue that a hammergun fitted with correctly functioning trigger blocking safety and Stanton patent rebounding locks is as safe as any gun that isn't unloaded!
At the end of the day, 'muzzle awareness' as our BASC puts it, is everything and as Greener said, 'the only safe gun is an unloaded one'.