From what I've read, the Mercedes BlueTEC system has some great technology. The injection timing and turbocharging systems sounds amazing, for instance. This system, though, has extra filters and scrubbers to get the soot and exhaust gases up to snuff. Do these need to be replaced or maintained regularly? Given the amount of junk that used to come out of diesel tailpipes in the '80s, I wouldn't be surprised if they needed frequent cleaning...
Also, I'd be a little worried about finding the the new clean diesel as my E light flashes. Is this gas becoming more available?