The Good: Light, low and slack geometry, very stiff and responsive, climbs and pedals very efficiently, clean cable routing, descends like a freight train.
The Bad: The bushing system requirements more maintenance than usual, but the bushings are only about $1 each and swap out quickly with out any special tools. Other than that, maybe a thru axle rear end?
I picked up this frame at a deep discount and built it with mainly with spare parts sitting around my garage. The fit and finish of the bike is top notch - no creaks, squeaks or clunks and the whole bike came together easily. On the trail its extremely fun. It goes uphill quietly with minimal pedal bob and has very good traction. Going down or fast through twisty, technical trails is really where this thing shines. It's nimble, quick and can be tossed through turns very easy. It's low bottom bracket rails turns and keeps the bike feeling stable over fast, chunky descents. The Spitfire is just as happy hitting jumps and drops as it is on single track. It's a very versatile bike, depending on how you set it up.
The bushing system isn't nightmare to keep up. New bushings can be bought in bulk for cheap and all you need to swap out the bushings is about 30-35 min, allen wrenches, grease, a mallet and a clamp. It's quick and easy and needs to be done once every few months if you're riding regularly.
Overall, the original Spitfire is still a blast even in the world of bigger wheels and fancy carbon.