I live in Springfield and Ken Grman is a very good Indy. I would recommend Coziahr in Decatur over Hall's in Springfield. Nothing wrong with Hall's but Coziahr is much more friendly and always act like they are glad you are there.
Walter bros. is in Peoria, never dealt with them. Usually go to Reiman's in Kewanee and I know an independent called Blue Collar Bikes.
I actually live in Kewanee... I go to reimans for most service also... however I think Weiblers in Davenport, IA. is a little better when it comes to service! Especially for engine work as Weiblers has a dyno and Reimans does not. Think Reimans customer relations is alot better than Weiblers though.