I think the coaster itself (or coasters themselves, as it’s duelling?) looks like quite good fun, if not anything particularly earth-shattering. While they’re not absolute favourites of mine by any means, I don’t dislike the Vekoma Family Boomerangs at all, and if I were to ride the two sides of Minifigure Speedway, I imagine my thoughts would be similar. This is effectively the same thing as Vekoma’s duelling Family Boomerang model, but simply manufactured by Zierer rather than Vekoma.
I do think that the overall finish with the mud everywhere leaves much to be desired, and the queue and station perhaps aren’t the most interesting theming-wise, but the rides themselves look like good fun, the duelling element should be good for capacity (even if Merlin appear to have repeated their airgate mistake from Mandrill Mayhem), and I’m sure it will be popular among the young family demographic, who are the target audience after all!
I think overall, the attraction will go down nicely and be a good addition to the park. Yes, the overall finish in terms of theming/landscaping definitely seems to be lacking at present, but Legoland Windsor did need a more thrilling coaster than the Dragon, and Minifigure Speedway appears to fit that billing quite nicely, in my view!