I believe that the 'Po-2' was indeed one of the most under-rated aircraft of WW2 - I am really enjoying reading all of your most astute dissertations & discussions and I should like to add what I can...
The Polikarpov U-2 first appeared in early 1927, it became the Po-2 on 30 July 1944 in honour of it's designer after his death on that date. The Po-2 was built in the greatest number and in more variants than any other aircraft in history, in excess of 33,000 aircraft. - At a rough count in front of me there over 35 different variants.- Not bad for a 100 hp biplane that served in a variety of different roles, most notably were the night 'nuisance' raids over German lines in Russia.- In particular those performed by the 46th Guards Night Bomber Regiment, who received 18 of the highest military honour of 'the Hero of the Soviet Union', 18 women pilots and 6 women navigators. It was the only regiment of 3 that was entirely of women, in the others, men also served - Polina Gelman, one of these HSU recipients stated that the 46th "was not only equal to the men's regiments according to effectiveness and other indices, but was among the first"- In further explanation, "the effectiveness was determined by the accuracy of the hits from bombing and shooting. After completing a mission everyone had to report their results and the results of others, as they saw them, what and where it happened. Crews from other regiments reported on our results, as did ground reconnaissance - in fact, we worked for them. It was easy to verify everything, everything was recorded: the number of combat flights, of bombs dropped, of rounds fired... In the 4th Air Army our regiment was always first or among the first."
- August/September 1942 it got really hard, renewed German offensive pushing into Stalingrad, they were attacking columns of tanks who were advancing so fast they had no time to change bases, shortage of maps, they couldn't harvest the grain so it was torched by Stalin's old order of "scorched earth" policy. It was at this time they read Stalin's new Order No. 227: "not one more step back"... As I too know, duty and patriotism come first in wartime...
Although the Po-2 carried only a light bomb load {120-200kgs & also 4x RS-82 rockets], the rugged reliability and it being based right behind the front lines enabled it to maintain continuous harassment of German troops throughout the year, even in bad weather. The Germans themselves admitted that it would be "wrong to underestimate the effects of the attacks, since they were so unpredictable and therefore were extremely disturbing...[they] reduced the already short rest of the troops and had an adverse effect on supply operations, although the actual physical damage done in the raids was small." - In actual fact, it appears from the two books I've recently read on Russian WW2 Aviation victory claims etc. they were most accurate. The first one was written by a IL-2 pilot who claimed they recorded everything as described above, and this book on the Women pilots, including the Po-2 'Night Witches', was written in 1993 by an American woman called Reina Pennington who went over there and intensely viewed records and interveiwed surviving veterans...
I agree also that the Swordfish was also greatly under-rated especially if you factor-in Taranto, and we should mention 'Hope, Faith & Charity,' these Gloster Gladiators who 'saved' Malta in the early WW2 Mediterranean conflict...
I also agree the P.40 was under-rated [by some], but they were a sight for sore-eyes when passing through Singapore off to join the AVG while RAF, RAAF & RNZAF had to make do with the most useless piece of crap that flew, the Brewster Buffalo. The US Navy couldn't get rid of their first monoplane fighter fast enough, dumping it on the British who promptly sent it to Singapore where they sent all their potty Senior Air Staff. - Should also add the Grumman Wildcat to the Most Under-rated list too, it saved our arse in the South Pacific along with the P.40's - And finally, the Hurricane was the first with 4 cannon, first with rockets, first effective Nightfighter during the Blitz [until the Beaufighter got it's gremlins sorted-out] and the Hurricane was certainly better at Singapore than nothing, the Ki-43 was definately under-rated by both the Brits & US initially, they kept mis-identifying it as a Zero, it just lacked the latter's cannons ~
I can recommend a REAL book about the Singapore debacle - ''Last Stand In Singapore - The story of 488 Squadron RNZAF'' by Graham Clayton ISBN 978 1 86979 033 2 -It's quite an eye-opener on what really happened...
Cheers