I agree. I was always sad that I never really got to drive my Allegro - my first car technically, though it died before my 17th birthday - so last year I went to look at an identical one.
Thoroughly disappointing. It handled well, was quite quiet, comfortable, and all that spoiled it as a 'modern' car was the speed - being a 1.3 it was slower than my 1.5HLS would have been.
Didn't feel like a classic at all.
Most underrated? FE-Series Vauxhall Victor VX490 (no slash) - 5 speed getrag box, in FI form (never released) it would have done (and did, on the development cars) 0-60 in under 7 seconds - in 1978...
Most overrated? Anything people blindly buy thinking it will be worth something, instead of just for the love of the car - presumably things like Ferraris, but more the concept, than the car. Every car is a classic, to someone.
Richard