I moved from 996 Turbo to E60 M5 when it first came out.

I did miss Porsche's direct handling feeling where you could feel even the pebbles on the road through the steering wheel and the acceleration of the Turbo engine, however, I emensely enjoyed the 500 horsepower V10 sound in a 4 door saloon M5.

Had a love and hate relationship with SMG, dual charactaristic of the M settings, great audio system and SatNav, much more comfortable suspension and a nice size boot.  Just much more useable compared to 911.

I could also drive and park M5 anywhere and nobody really cared as it was just another Bimmer.  I could always find a reason not to drive the Turbo during ownership, while I could drive the M5 for every occasion.

But, you do not get that special feeling that you get with Porsche and you WILL miss it.