Haven't bought any of the recent upgrades only as I've skipped out on CW as I dislike the idea of the primary toy looking very incomplete without the upgrade.
Maketoys has been around for a while and has historically held great quality standards. I've bought quite a few 3P and this is how I would rank them:
1. Fansproject
2. Maketoys
3. Mastermind Creations
4. Perfect Effect
All 4 have very high standards of plastic quality - all better than the latest grades that Hasbro uses. The rankings for 2/3/4 are very close and a bit harder to differentiate - however I take into account proportions and designs which affect a toy's overall balance. For MMC, Feral Rex and Hexatron were very G1-like and slightly clunky (not a problem if that's what you like), as well as some very tough joints to move around; whilst for PE, I'm referring to the transformation for Warden, which was a bit finicky for me.
The only issue with Quantron I've read about is from fellow Ozformer, liegeprime, who had a factory construction issue (not related to quality/mould quality). I think he was given two left parts for a part of Sonic Drill's leg joint.
Edit: Here we go: http://www.otca.com.au/boards/showth...t=19423&page=2