Well, to add my own thoughts to this, which echo a lot of what's said already...

*Ahem*
As with just about everyone else, there's no 'set' thing that will cause me to either buy or not buy a third-party product. But there's some stuff that comes up..
1. Almost all my TF collecting nowadays is funneled into Classics/Neo-G1 or Masterpiece, so would this purchase aid my goal? Those TF:A Huffer and Pipes figures aren't getting bought by me, no sirree. I'm also not purchasing any toys that seem to be Masterpiece replacements. That's for official product only.
2. Has Hasbro or Takara already put out something that suits that character already? Toyworld's Bumblebee is almost laughable. I've got about twenty versions of him already, not to mention the upcoming Masterpiece version I've already got a pre-order for!
However, I also don't suffer retroactive regret. I love my Warbot Defender and still consider him to be great. He
and Hasbro's Springer are on my Classics shelves.
3. The company putting it out is a determining factor, too. Fansproject, Perfect Effect, Mastermind Creations, I haven't regretted any purchases from them. I honestly don't get the hate FP gets nowadays.

Other companies, though, cause me a bit more hesitation. TFC isn't too bad, but the fact that Uranos
seriously needed an upgrade kit bothers me. I've been burned too much by iGear, too.
4. Price, natch. Genesis looks cool... but he's
way too expensive. And to bring back to point two, YOTS Omega Supreme is fine as my Classics Omega.
So, there's my criteria. I added nothing to the conversation!
Not caring about scale since 1984. Just like Hasbro.