like others have already said, look for DOT approved. the brand i'm aware of is Goodridge which is carried for MBs by Performance Products in Northridge, CALIF.
my friend has it in his car and the brake feel is definitely different, takes some getting use to. in my opinion, not as comfortable for everyday driving. it eliminates the lag or cushy feel of the brakes, but it is firm. it provides quicker brake response which can be jerky for everyday driving...
OE rubber brake lines last the life of the car, so SS should definitely last longer and would not require replacement under normal use.