My take on this: I am slightly concerned about Full Auto, but many of the various suggestions have some problems with them.
Now, I do think it is odd that full auto(and semi-auto) give both a bonus to hit and full extra hits (many systems I have used in the past have given a bonus to hit and bonuses to damage, but not extra hits). It also seems a bit odd that fully auto-gives both a higher bonus to hit and gets more hits per DoS than semi-auto. However, the fact that it makes it more likely to hit the target in the first place is not that strange, so I don't see a problem with the bonuses to hit, or fully auto getting a higher bonus. By firing more shots in the direction of your enemy you are more likely to hit. Burst fire on modern automatic weapons is explicitly designed to make them "more accurate" at medium/long ranges (and at shorter ranges to give them greater chance of defeating body armour/putting the target down as they are hit by more than one shot). Fully automatic weapons are, in the end, more likely to hit a person occupying a specific area than semi-automatic, though obviously at a much higher cost in ammunition.
Personally, the original DH rules actually seemed not that bad (even if they were the result of a failure to update them after playtesting, as I have heard), ie that both semi and full auto burst got hits on 2 DoS. That means you are more likely to hit with both than single shot, and fully automatic is even more likely to hit again, but most of the shots will likely be wasted (rather than getting 6 hits with a good roll you will be getting 2/3), though the potential of much higher damage output is there. At the same time I am not keen on allowing the players to move while firing burst fire of any type, as that kinda should be part of the pay off between those modes and single shot ("Do I move and get a lower chance of hitting, or do I stay where I am and use a burst).
Also, remember Full-auto burst really does just represent an extended burst, or even a couple of more normal ones. Fully automatic weapons are capable of more than 10 rounds in 5 seconds. That is more like a single second extended burst, or 2/3 shorter bursts of 3-5 rounds. If anything it represents quite deliberately taking down a target while taking advantage of the capabilities of automatic weapons. Semi-auto is really a few shots fired semi-auto, or a single shot of a weapon fired in burst fire, both increasing your chances of a hit. Single Shot more represents a single quick shot that you take while doing something else (or, if using Aim, one single very carefully placed shot). Standing there just emptying your magazine at the enemy would fire a whole more shots than any of the weapons actually allow you to do.
At the same time I believe Black Industries intended money to be much more of a balancing factor than FFG's have since. For example, the rather lackluster performance of lasguns has been mentioned here, but they do have one major advantage over SP weapons: that after you have bought ammunition for them you pretty much don't need to bother ever buying any more. Combined with making players pay for stuff like where they sleep and their food. Now, looking at the wages and the cost of many things are just stupidly priced (the various drinks and drugs being the main ones), but I am starting to wonder if the cost of food and sleeping arrangements at least was intended as a per party figure, rather than a per character. At that point it becomes affordable, and leaves very little for the characters to spend afterwards. Having to buy ammunition frequently would be a pain, and would severely curtail any move to the auto-fire setting too often. Just having the Inquisition pay for their ammunition removes this limiter and kind of does mean las weapons loose their purpose. Now, Yes, eventually they probably would, so if you are playing much higher level campaigns I guess this advance is useless, but at lower levels characters should be scrimping and saving at every opportunity.
Now, I don't think lasguns really do need anything else. 1) On being more accurate. This is not that true. The main limiter on the accuracy of small arms is not the weapon itself but the person carrying it. Experiments done with lasers have shown that individuals are not really any more accurate than if equipped with projectile weapons. Now, at extreme ranges, like those used by sniper rifles and the like, it might start to have an effect, and it probably would on mounted weapons, but not on normal small arms. 2) Lasguns should normally not have autofire. Yes, Dan Abnett has them with autofire (and recoil) but then he misses much of the point completely. He has different sized lasgun packs (when the whole point of the Imperial Guard has always been its standardisation... a charge pack is a charge pack, at least for similar classes of weapons). He also has them running out of ammunition. I don't mean in combat, that's fine, but in the same book as the previous incident they have to scrounge their remaining charge packs while at base... rather than just recharging the ones they should always have on them. Gaunt's Ghosts is full of these nonsenses, and so are best viewed as generic sci-fi war stories with a little spattering of 40k.
The Uplifting Primer, on the other hand, gives the lasgun's cyclical rate as being about 150 rounds a minute... ie, barely even fully semi-automatic.
Oh, and on guys being "thrown back" by being hit: This does not mean that las-weapons are not lasers. Even with bullets it seems that the vast majority of the movement experienced by the body due to being hit is actually the body reacting to being hit, not momentum being transferred from the bullet to the person.
