I have driven a Leon recently and it drives very similarly to the Golf but the interior really let's it down.
I'll echo that. I drove a FR 2.0 TFSI DSG recently, and whilst it was a cracking car, it was let down by it's interior. You'd feel pretty short changed in the Leon compared to the Mk5 Golf it dates back to, let alone a Mk6.
I used to have a Mk4 Golf GTI and changed it for a Leon Cupra in 2002. I gained 30 PS, another cog in the gearbox and a few other extras, but the quality of the interior felt like a step backwards.
Having said that, I guess it's all reflected in the price.