I have a 7:1 Harken system.
Before I had a Dart 18 with its unique twisted block, and a traveller with rollers instead of sliding balls (I forgot the company). In all respects the system on the Dart was better:
*No rust inside or outside, after 14 years sailing in salt water
*Never needed to lubricate or clean any part, again after 14 years in salty and sandy environment (I have to spray sailkote on the Harken traveller system every month).
*On the Harken block the angle adjustment of the cleat is too coarse, I can't find any satisfyng setting

I guess most people are satisfied with Harken and other supplier, because they never have a chance to compare to other.

Cheers,

Klaus