I've only flown one 4-tank PA28, it was a PA28-235c (Cherokee wing, 4 tanks, fixed gear, variable pitch prop, 235 hp Lycoming). Cruised about 140kn, "sipping" fuel at about 40 litres/hr (that's about 11 US gal/hr) when leaned for cruise !
The fuel system was similar to the conventional 2-tank system, except that there were 4 small fuel gauges partially obscured by the yoke, not 2. And of-course, the (not in clear sight) tank selector went 5 ways rather than 3. The risk of selecting the wrong tank, particularly if cruising low-level and thus trying to keep your eyes out of the cockpit as much as possible, was in my judgement quite high. (Well I did it once anyhow!).
I agree that the PA38 fuel management panel is a huge improvement on anything fitted to any PA28 I've seen from the viewpoints of visibility, clarity and ease of use, or for that matter most Cessnas. I know it's high and obtrusive, but why it couldn't be incorporated into later PA28s is beyond me.
G