I have refrained from getting into the SA80 is shit arguments as I disagree with most. For the first 13 or so year I used an SLR and for the next 12 an SA80. Most of my operational time was with the SLR. I was a competent shot and represented the Bn at NECIC (75) and Bisley (77). I was SAA instructor from 78 to 98. So my experience with both weapons was extensive.
Left handed firing – in reality it was a bit like firing using the respirator, we all did it but had difficulty hitting any thing smaller than a fig 121 at 100m. it is nice to have the cover and the threat that you can return fire from the left shoulder, but you are unlikely to hit anything especially as you would probably be standing supported or kneeling supported. When moving and covering gaps (urban) it was useful to change hands but to turn and walk backwards was just as simple.
Weight of weapon – not much in it and as I had grown up always carrying (16 Junior soldier) a rifle in my hands, never get caught with the rifle slung unless both hand are full and over flowing, it was no real problem. With most of the SA80s weight in the back and closer to the body it felt lighter. The most startling concept was that you always used the sling on the SA80. This mad a big difference to the weight and ensured it was always to hand. The main advantage was the ammo load and speed of reloading mag if you had a nice small US loader (her name was Sue). Fitting the bayonet made a very big difference to the SLR with weight and firing. Also the early bayonets on the SA80 had a habit of bending, we had a number bend and some break when in the US. Overall the adoption of the sling made the real difference.
Serviceability – I never had a problem with the SLR except when we had captured argie ammo for training. I was very happy with the SLR and got to the stage where I could tell the type of stoppage by the feel of the trigger. The SLR was not perfect, it stopped, you carried out the IA drill, it worked. I never encountered any real problems with the SA80. This would fly in the face of what is said by many, but I never saw any great difference to that of the SLR, it stopped, you carried out the IA drill, it worked. My Bn was in the first wave to get the rifle in 87. The problems encountered were mags, old US colt mag that went gold very quickly. When they got replaced feed problems lessened and capacity of mag went up. The mag release catch was a problem caused by its location and how the weapon was carried. This was over come by one of our armourers making and gluing a guard on the side of the rifle. He got a payment for this mod. I think the location of the mag release had more to do with buying mags off the shelf then ergonomics. A method that was used by troops was to have string attached to the bottom of the mag and clipped onto the rifle so that if it did fall off it was attached. We had the occasional num nuts who put the gas plug in the wrong way and the return spring flying through the air on occasions.
The small plastic square used to release the holding open device was crap, but I got use to using the holding open device to release the workings. Never had a problem with the cocking handle, the one on the SMG was deadly.
I loved my SLR a real rifle, I also loved my SA80 it served me well.