So far, as a fairly recent modeller, I have been very impressed with the Walther's Cornerstone Kits. They are well worth it. Take for example Interstate Fuel & Oil, which I just completed.
I loved that kit for the reason that it is so flexible, and can be arranged to fit almost any space. It really shows immense detail for the structures too.
Here's the office building. It might not be much, but I painted it and weathered it as I saw fit. I was very pleased, and assembly didn't take long. For me, it's the painting that will kill ya. (i.e. each individual pipe!)
Not only this, but I was so happy with Walther's, I bought the new City Station, which is being assembled as we speak. It looks great, and construction has been an ease.
So, in summary, I would highly recommend the Cornerstone Kits. Don't give it a second thought, they are certainly A+.