Beyond the amazing power of its upgrades, this level 0 creature can act as a resource generator. Uncanny Growth has no limit to how many growth it can put on at once, meaning you can turn each point of success into a resource.

Looking at the cost analysis:

Cost: 4 actions (to play, get event, investigate, get resources), 2 resource cost, ~2 cards to commit.

Benefit: 1 clue (~1 action), 6 resources, 1 health/sanity.

Result: -3 actions, +4 resources, -2 cards, +1 health/sanity

which is not worth it, compared to other cards that generate resources.

For a big-Money deck that focuses on high skill value, it might be worth it. For instance, in Jenny, who can take Streetwise, each cycle (get Uncanny Growth, play Uncanny Growth and boost with Streetwise, get resources from Myconid) would increase her resource pool by roughly 50%. Though, woe to the person that draws an autofail (maybe bring Justify the Means?).

Just wanted to point out that because Uncanny Growth is an Insight, it works very well with Crafty, which is already one of the best tri-class talents from EotE. With an upgraded Myconid it is almost pure upside (discounting situations where you cannot or are punished for playing events) as you can make Uncanny Growth free with 1 resource then test at +1 with the other.

Fits very nicely into the Ice Pick-Scavenging loop and other Insight-heavy decks (e.g. Joe Diamond). Big hand Seekers may also want to get into horticulture, especially Harvey Walters who can easily use Farsight on Uncanny Growth and would appreciate Nurturing Strain's soak for damage from his weakness and horror from deck reshuffling.

2x Ariadne's Twine 1x Cryptic Grimoire 1x Dr. Milan Christopher

Congratulations, now you get 1 actionless Investigate that charges your Myconid every single round. The Myconids seem likely to get Taboo'd pretty quickly to me, especially the Sentient Strain. It is incredibly easy to game these things out and trivialize an entire scenario.