Here's my experience as a newer owner. I've had my 05 SRT6 for about a yr and 12k miles. Got it at 48k and its now at 60k. Using it as a daily driver, except when its raining or there's snow on the ground (I have an explorer for those times)

milage has been in the mid 20's mpg in moderate traffic while driving reasonably, ie. usually 10 over the limit unless I breaking out of traffic

no problems except the door locking pump (know issue) although I will probably have to replace my IC pump soon. Most if not all issues have already been covered on this great forum.

I must say, oil changes have been much cheaper than I expected (quoted $160 at the stealership). I get the mobil 1 when its on sale for $6/quart ($54) , oil filter is about $16 on ebay and I found a independent mercedes shop near me that charges me $7 to change it for me. Originally they quoted me $20 for the oil change but each time I've taken it in, the mechanic charges me .2 hrs, I think he likes working on it

Anyway, I like it so much I bought a 2nd one, although it is a rare 06 SRT6 that lives in my garage. So in a yr, I've gone from 1 car to 3 cars....

Best of luck.