Good: spacers increase the track = better turns, cheaper than new wheels
Bad: just spacers incresase the scrub radius, increasing torque steer, and put higher loads on the studs / hub

Ideally you want to grow the track "out" and "in" in equal amounts, but that only works with new / wider wheels and likely rolled fenders. Spacers are a viable solution if you cannot find the wheel you need/want in the correct offset, and the resulting srub radius is still comparable to stock. With spacers alone I wouldn't go past 15 mm or the car could become "twitchy". That being said I have only reading knowledge on the subject, and have not used spacers myself yet..

The June issue of SCC has a good article on suspension tuning that explains a lot of this.

 

does anyone if a +45 offset wheel with the H&R 15mm spacer/longer studs would fit the Evo8 without problems? I'm thinking the wheels should not come out past the fender and it should look like a +30offset wheel. Please let me know. I have a set of Blitz Technospeeds left over. I'd love to throw them on the Evo