It came late to the war, and I wondered at that stage how either side reacted to it. It didn't do too well in battle, and I wondered if the soldiers who happened to see it, especially those knowledgeable about tanks, thought it would be a new hope for the German army, or a waste of materials.
A number of books have something to say about this.
Mitchell, in his memoir Tank Warfare, sounds quite delighted to finally see his German adversary and was quite excited to open fire on them.
Other books say that the British soldiers reacted in the same way as the German soldiers, ie they ran away in fear.
Most British books say that so far in the war, German Command had been belittling tanks and saying they were useless and nothing to be afraid of, and having very little impact on battles, tactics and strategy. For High Command to suddenly completely contradict themselves and start paying attention to tanks and tank tactics must have seemed very confusing for the German Army: how could their infantry be expected to have confidence in their own tanks when they have been told repeatedly that tanks are no good.
And one of my books says the 18 man crew were from different arms of service, and held the other arms in contempt, meaning communication within just one A7V was extremely poor.
So an already woefully inadequate design was rendered even less effective than it otherwise could have been by poor intra-tank communication and the psychological undermining by High Command.
The appearance of the A7V did have a marked reaction in the Tank Corps however, who realised that a gun armed A7V was more dangerous to a Female than the other way round. This led to the conversion of Females to Composites (Hermaphodites). At least one Battalion was equipped entirely with Composites and Males - effectively the A7V rendered the rhomboid Female obsolete.
The notion that tanks were no good on the battlefield was dead - on both sides - after the Cambrai battle. The A7V was unusable in trench warfare, but after March 21st, 1918, fighting moved to open country mainly. Here, the A7V was superior to the slow Entente designs, and better armed. This, however, was offset by the miniscule number available.
Those German soldiers seeing an A7V generally were very pleased (but this is also valid for captured Mk.IVs), because the presence of tanks could save the blood of the infantrymen. However, the vast majority of German soldiers didn't see a tank at all during the war, and even fewer saw a German tank.
That the German supreme command recognised the value of tanks is documented by the plan for 1919: production of 4,000 LK IIs (thereof two thirds gun armed) and 400 heavy Oberschlesiens, plus use of about 170 captured Mk.IVs and 10 remaining A7Vs.
The example of German 17th Amy shows that also the field commands were well aware of the value of tanks. Hard pressed by the British 100 Days Offensive, they constantly asked for German tanks, despite heavy tank losses because immobilised vehicles couldn't be salvaged in time. Their rationale was that the presence of own tanks decisively improved the morale of the infantry - and that counter attacks without tanks were doomed to be called off before they even started.