The Greif is historically lamented for its early stability and engine problems, but the fact is that by the A-5 model these problems were ironed out and the He 177 had proved itself to be the most technically advanced bomber of the Luftwaffe. The RAF were impressed by the postwar tests on the He 177 A-5 and the single long-range He 177 A-7 they captured. Another very advanced bomber, the B-29, also had a reputation for catching fire, and also took two years to have its problems ironed out, after which it became one of the most successful bombers of aviation history. Unlike the B-29 the He 177 never got the chance to show its full potential due to the misfortunes of war.
He 177 A-1
First production series, 130 built. Stability problems. Engine problems.
He 177 A-3
Second production series, 170 built. Sixteenth and subsequent aircraft powered by DB 610 A/B engines. Engine problems. Structural problems.
He 177 A-5
Main production series, 826 built. Strengthened wing, shortened undercarriage oleo legs, increase in maximum external bomb load.
Those 300 A-1's and A-3's are largely responsible for the Greif's unfavorable reputation.