Yeah, switching from the original 13-24 Suntour freewheel to a 13-28 SunRace made a big difference. The SunRace shifts better and runs quieter too.
Biopace was okay for me when set up properly. I rode the 52/42 Biopace road double for about a year, first on a Trek 5900, then on my Ironman for a few months this year. I liked Biopace with the right crank length after strengthening my legs and slowing my cadence from 90 rpm to around 75 rpm.
With round rings I can get along with cranks from 170-175, no problems. But with Biopace I liked only 170 cranks. When I tried 172.5 I started getting knee twinges, and the eccentric rings felt herky-jerky, surge-y. Switching back to 170 fixed that problem.
I understand what the fellow meant about downtube shifters. I use them and like 'em, but they do take some familiarization. If I go awhile without downtube shifters and use bikes with brifters or something else, the downtube shifters feel a bit awkward. Takes practice to shift smoothly without affecting balance. And downtube shifters will always be a hindrance on climbs that require lots of shifting. With brifters I can shift while standing and not lose momentum. With downtube shifters I need to sit for a moment to shift, then regain momentum. Over time and distance it costs more energy. On reasonably fast group rides that's where the group usually gapped me -- on our many short, steep climbs, I'd lose momentum with the downtube shifters, or burn up my legs quicker grinding and mashing bigger gears rather than shifting. Brifters are quicker in some situations and conserve energy and momentum.
I've ridden my Ironman exclusively since disassembling my other bike in February. Just never got around to finishing the rebuild. But I have no complaints about the Ironman. However, if it was my only road bike, I'd probably switch it to brifters. And upgrade to at least an 8-speed cassette, or more.