Okay, I guess I'll start and you all can critique my opinion.
Having such a cheap and effective rocket at the beginning of the war would make ground attack pretty effective, even more so than it historically was, as the fast Me109 that did strafing could now contribute accurate rocket attacks on tanks with a good chance to knock them out. Stukas too could use them, though the Bf110 probably would have some trouble due to the wings being taken up by engines; its probably just easier to use the cannons and center line mounted bombs. FW190F and Gs become a lot more effective starting in 1942 when they are introduced, as they have a weapon that can accurately be used as high speeds. Probably bad news for the Soviets. In terms of bomber killing in 1942-43 it makes the Destroyer concept obsolete, letting the Bf110 and Me210/410 more useful as nightfighters, long range escorts (in the Med.), and as bombers/recon. Me109s can be used effectively to bust up bomber boxes on their own without much if any escort, while the FW190 can focus on lower altitude operations, rather than having German fighters struggle for high altitude performance with bomber killing cannons that made them sitting ducks for allied fighters. No need for big wing form ups that got them smashed up by Allied fighters in 1943-44 as they were assembling, rather they could attack in small groups with shotgun hit and runs from higher altitude dives and speed away before escorts could get involved. Rinse and repeat until the boxes are broken up and bombers can be picked off by small groups of fighters. Its much harder to counter than big formations, which can be dealt with by fighter sweeps. It would lower Luftwaffe losses significantly, especially with the two engine fighters, and may cause cost prohibitive losses to USAAF bombers, while delaying the end of the LW due to the P-51D not having easier targets en masse. No need for things like the Sturmböcke, so most LW fighters could focus on anti-fighter armament and staying light and maneuverable.
This probably also eases the transition to fighter-bombers and fighter production over standard bombers and Stukas. Perhaps the Ju87G doesn't make an appearance?