The factory repair kit for the carb (WT-1009) on my Echo is like $10. Should I ever need to replace it, I would just go with this one - assuming that Walbro has a kit that fits my carb (which it doesn't look like they currently do). If I'm tearing the carb down that far, I may as well spend a few $$ more to never need to do the job again. It's an extra $10. I've spent way more and gotten far less for it than the $10 difference between the "conventional" metering setup vs. this new whiz-bang spiral thing.
With that said... My Poulan (circa 2005 with its Zama carb) still has all of the original factory carb parts installed and I have had no problems with it at all.
I do run non-E fuel. Perhaps that's the secret.