I run a C63, but came from a 325i (not 335i) albeit via a CL55 inbetween them.
If you've driven one then there's not much I can tell you about driving one that you don't already know; they are ferocious in pretty much any gear.
Make sure you spec a LSD as they are keen to light one wheel up in pretty much any of the first 4 gears in any conditions under WOT. If you buy the lower state of engine tune (circa 450-ish) you can release the full fat 500 via an Evolve remap.
Fuel and tyres will be your highest consumables and the amount that costs you will obviously depend on how you drive. This morning on the way to get a new tyre with a space saver rear on dictating I did max 55mph (blowout on M1 yesterday) I managed to achieve nearly 26mpg. I've never before seen economy like that on this car, but driving everywhere at 55 is boring as shit, so I'll never see it again.
Quick driving will see you average about 19mpg.
Fast driving will see that dip to 14.
My rear tyres has lasted on average 7k between changes.
I'm due a big service in 1000 miles, so i'll let you know what that costs. Previous services have been no shockers - average stuff.
Only failure so far on 36k miles is the power steering pump which was fixed inside of a couple of days by Merc of Cambridge.
I still love the car as much as I did on day one. The only negative is the 60 litre fuel tank - with the 'economy' the range is proper crappy - I spend a lot of my week stood on forecourts. My quarterly fuel usage for circa 20k per annum is about 1300 litres.
I would agree on the comment re lease deals, but pay attention to the t's and c's - if the deal is via Mercedes corporate, then it'll be an a operating lease, so that won't include RFL beyond year 1. Second pint is, most of the deals at that level are base model cars - add the basic (required) options of 19's, Harmon Kardon, COMAND, privacy etc and the monthlies will easily rise to £700+
Gone but not forgotten:
325i M Sport (E92), Black Sapphire, Coral Red Dakota, 19" 225's, Seat Heating, 6FL and de-badge
Replaced by 6.2 litres of AMG powered C class.