I ordered my '11 535ix with the standard suspension. It also has the standard ZF eight-speed transmission, so I cannot offer you a direct "apples-to-apples" comparison. However, in this configuration, I would not describe my vehicle's hydraulic steering as "heavy." Moreover, it certainly is not as "heavy" as the steering in Mrs. bimmerific's '08 335ix coupe -- but it does feel "connected" to the road, and registers terrain compositions and conditions very well.
His: 2011 535ix, Dark Graphite, Oyster/Black, ZAV, ZCV, ZCW, ZPP, Nav & Some Goodies
Hers: 2008 335ix Coupe, Space Gray, Dakota Gray, Loaded, Special Ordered ZKS (the Kitchen Sink)