This topic has definately wandered off into the woods but in attempt to respond ...
I recently purchased (as I mentioned in another thread) a 2007 Acclaim, right in time for the Zombie Apacolypse ... I put it in for the annual and I have no idea when I'll see it again although I already paid for it. In any case, I started out looking at Lancair's to go far and fast but ended up wanting a certified plane due to regulations here in Brazil that give some limitations on experimentals that are probably liveable if you are out in the sticks but not so much living in Sao Paulo (your experimental cert prohibits flights over most populated areas and Sao Paulo certainly counts) ... but I was trying to figure out out at the time if I got a Mako or an older ES if I could put one of those Continental diesels in it for all the reasons already discussed above. The cost and availability of Jet-A plus the challenge of doing overhauls overseas make the pop-it-out-and-replace-it 2000 or 2200 hour TBO liveable. The restrictions on the flights, though, make it tough to swallow here.
If there was ever an STC to put a 250-300hp Turbo diesel in and sip Jet-A I would be all over it. The big Conti engines aren't STC'd for anything that I can find and they are heavy (someone said 50 lbs but it seems more like 100) ...
On the performance side, though, I was reading Aopa Pilot back issues the other day waiting for the world to end or get better and they put the 172S head to head with the diesel version that Cessna briefly offered and with less nominal HP iand it flew faster, had shorter takeoffs, and burned less... so with nominal horsies at 155 for the Conti CD-155 vs. 180 for the IO-360-L2A that powered the conventional S model. While not impressive vs. a Mooney, the diesel powered was 132Kts true at 8,9GPH at WOT and 124KTS at 7,1gph at 80% power or 112 at 5,7GPH at 70%. The stock 172S has a normal cruise of 124 Kts @ 75% (WOT @ 8500ft) burning 9,5 gph of Avgas or 115 KTS @ 65% power burning 7-8 gph (I don't remember) ...
Point being I don't think you would lose any airspeed up front and the economy would definately always be there. If anyone comes up with an STC to go diesel, even if I had to switch to an earlier airframe, I'd take a look.