It will be a big shock to your system mate! hopefully in a good way.
I have never owned a car as modern/refined/fast as your beemer so cant really compare, but i have owned a few old Fords and driven them every day. I currently use my modded Capri every day, 20 miles each way to work and bombing around in the evenings and weekends. The interior is stripped out, shes got stiff suspension, no radio, the heater just about keeps the screen clear if i keep the window open a bit, 80 odd horsepower 1.6 pinto and a 4 speed box so its not a 'pleasant' place to be. BUT, I get excited every time i drive her which turns every cold, grey, dull morning comute into a special occaision. I wouldnt want to drive anything else.
Lotusless does make some good points though, the state of the roads now will slowly destroy an old car if the maintenance isnt kept on top of. You should be carefull where you leave it, i always try and park near a CCTV camera and if i have to leave her somwhere slightly dodgy i will pull off a couple of HT leads or take the rotor arm off the dizzy.
At the end of the day what have you got to loose? try it out, modify it to suit your needs, get another daily driver if you have to, get something different all together if you dont like it. Personally i think youll love it