I've been considering this for a while. My '99 is at 120k and will likely be retired to track-only/fun-car duty in the not-too-distant future. At that point I have to decide whether a few grand in upgrades trades against the kit price, and if another project fits into the timeframe.
A few comments/opinions:
-The concept is great: cheap, simple, easy kit car. High performance through light weight.
-The value proposition for building one in the US isn't as good as in the UK. The kit cost here is roughly 50% more than there, after shipping and paying US distrutor.
-Many people complain on the appearance, but to me it is a track tool and I dig the minimalist approach.
-I haven't seen one in person, but from internet pictures the construction quality appears to be in line with its cost - not great but good enough.
-The "M" rollbar is a no-go, and even the upgraded "MSA" rollbar scares me for the track the way it is fixed to the car (bolted to corner plates which are fillet welded and loaded in bending). It is also very narrow. I would order one with the bolt-in rollbar, throw it away, and weld in an integral bar right to the main chassis spars.
-Some of the chassis fabrication, particularly in the front strut area, looks like it could be improved. Most likely could be fixed prior to paint or powdercoat.
-The requirement to run huge wheel spacers in order for the fender stays to fit right is silly, and adds risk on the track. Maybe this has been fixed.
-I would probably go for the lightweight option (ditches the Miata subframes), but it isn't cheap
Realistically to finish one here with decent parts you are getting up close to 818R territory price-wise. The 818 is heaver, consumable costs will be higher, but has a lot of growth potential. Also looks safer.