Conway was a working pro. He wrote some good things, some excellent things, and a ton of crap. Just like his contemporaries. The last good comics I read by Conway, for the record, were Cinder & Ashe, The Man Thing story from Savage Tales #1 (which was a better direction for the character than the Gerber stuff, imho), and parts of Atari Force, which is a pretty good comic for being essentially a toy license book. He was a working writer with many highs and lows, but I don't think it's accurate to claim he never wrote anything worthwhile.  

I liked his Thor stories too, even if they played it loose with continuity. They had just the right blend of mythology, SF and comic-book craziness.

He followed Engelhart on Avengers but it was temporary and had the feel of just fill in status. I thought he did fine work on many books in his career. He also hacked out crappy books just for a paycheck. 

People forget that Conway was only 19 when he took over Amazing Spider-Man. 

In Conway's own words:

"Precocity is a well-known curse; most of the pressure I felt as a younger writer was self-imposed. I wanted to be accepted by other writers and artists as an equal, which put me in some awkward situations — pretending to be more mature than I was, emotionally and professionally. As it happened, I was pretty good at faking a maturity I didn't have, which had advantages and, obviously, some disadvantages. I think people often forgot how young I was, and expected me to perform at a level that was actually beyond me. The result was, I was pretty stressed for most of my early career as a writer, and I often felt like I had no idea what I was doing —which was true. I wrote instinctively and from the gut; when those instincts were appropriate to the material I was writing – for example, when I was writing [The Amazing] Spider-Man — the results were something I was quite proud of, then and now. When my instincts were off, I didn't have the experience to either recognize it, or to compensate for it, with results that were more uneven."

Just finished Conway's run on Daredevil (admittedly I skimmed a lot of the text) and it certainly didn't start out great, continuing a lackluster tradition for the character begun by Lee and Thomas. His habit of DD referring to himself in the third person as "Matthew" in thought balloons drove me nuts. Much like his later work on ASM, he goes for a major shakeup (not as extreme though) by bringing in Black Widow as a partner/love interest and jettisoning the previous supporting cast. This is also when he relocates the series to San Francisco. So kudos for changing things up. The stories don't really get that much better, with DD moving from one mystery villain to the next, a trope started by Lee early in the series. The resolution of the Mr. Klein mystery in particular, which crosses over with Iron Man, is just plain bizarre but gets bonus points for uniqueness I guess. All in all, a memorable run for the status quo shakeup but that's about it. The villains are mostly uninteresting. Widow as drawn by Gene Colon is gorgeous though. Conway was super young when he wrote this, so I can't be too harsh on him. I think I preferred this run to Thomas' and maybe 50% of Lee's time on the book, which kinda tells you how consistently mediocre 60s/early 70s DD was

I agree. Perhaps 70's Superman is an acquired taste, but I have acquired a taste for it.  It's some good, goofy reliable fun. Sort of like comfort food.  Also, like you, I love the fact that they're one and done. I can grab and random 70's Superman title I see and feel pretty confident that it's not going to be continued, making me feel like I have to go out and get the next issue.