I bought my STI four years ago. It was stock, yet still quite fun. I bought the car as I am an avid Subaru fan.
I like the fact it offers a raw driving experience, even when unmodified. The big STI wing on the back looks fantastic, and all the little STI emblems on the inside of the car look great and really set it apart from the WRX version.
The car is lacking technology, although for its age it will do. I don't think anyone would buy this type of car to do anything but enjoy driving. It does come with climate control but it feels cheap – the temperature control is in the form of a knob!
The 2.0-litre turbo flat-four is fantastic combined with the six-speed transmission, and there is quite a lot of torque for such a small-cubic-capacity engine.
As stated, I have owned the car for four years now with next to no major issues with it. I am a mechanic, so servicing is relatively cheap.
The improvements made by Subaru to date have been a step forward in terms of technology, but you can't beat the raw, uplifting feeling of driving an older STI.
The Brembo brakes from the factory are much better than the standard Subaru brakes on the WRX version. The intercooler water spray helps when driving in city traffic. I can notice a considerable difference when using the spray compared to not using it.
The all-wheel-drive system sticks to the road like no other. Coupled with a set of good tyres, this makes the car really stick to the road in all conditions. Although the 2003 model is missing the driver-controlled centre diff of the new-model STIs, I feel that the transmission still does a great job of delivering even power to the front and back wheels.
In summary, if you want a car that ticks all the boxes in terms of performance and handling, then make sure you take a look at the older STI as its bang for your buck is fantastic.