Speaking from personal experience, a salvage title can be either a death knell, or a wonderful opportunity. Overall, Karl is right -- it means the car's value is pretty much automatically reduced by 30-40%. I think a salvage title has a black mark on it that is often times very well deserved, but sometimes not so deserved.
It all depends for what reason the salvage title was awarded. If you can get documentation that the salvage title was given for a very minor thing, like a bent fender or such, that would be easily repairable, then it's a good thing because the damage can be easily repaired, and an otherwise great car can be kept on the road (albeit with a salvage title black mark). I've seen a lot of cars with hard hits get salvage titles when they were still young and quite valuable, and the car was repaired because the overall value was still more than junking it. Our E500Es are nowadays way past that point, so salvage titles are awarded for very minor hits and accidents.
When you get one of these cars that was hit back in the 1990s and was repaired -- and you can tell it was a serious hit -- then it's something that you should run away from. Unfortunately, owners seem to want to "deep-six" this type of information so when you see a salvage titled car, you almost NEVER see or have any information about the actual damage inflicted on the vehicle nor the repair. You just have the title with the black mark on it.
I personally have purchased a couple of salvage-titled MBs (my 560SL and my 1995 E320 wagon) where I fully knew, through photographic evidence and direct contact with the person who repaired said vehicles so I knew the extent of the damage and had evidence of it. In both cases it was minor damage (the wagon had a simple, easily repaired fender damaged with nothing else; the SL had a bent A-pillar which required a new factory MB A-pillar, windshield, and a new factory dashboard, no body panels were touched) and thus I was 100% confident in the integrity of the car. But this is almost never the case, and I would not have purchased either car had it not been for complete knowledge of both the issue and the resolution. It also allowed me to get both cars for a song (the 1987 560SL, particularly, only had 45K documented California miles on it) and of course I've never had any sort of abnormal issue with either car. I didn't buy either car to resell it though, but rather to keep and enjoy and drive for many years to come.
My advice with regard to salvage titled cars is to avoid them unless you get solid documentation, proactively from the seller, up front, about the issues with the car and how they were resolved. The issues have to be minor/cosmetic, and NEVER structural. If structural, a hard hit, etc. or there is little/no definitive information, then I'd run not walk away from any seller.
Life is too short to deal with accident related issues. As with any car purchase, choose carefully, and know what you are doing/getting into. If you do your homework and have good information, you can do quite well and get a very nice car. If not, you will have a bundle of problems that will never (and I repeat NEVER) be right even if you throw bundles of money at it.
Cheers,
Gerry