In some ways I look at platinum as a better investment than gold because of its utility in industry. However, that's a downside, too. Let's say the economy tanks which drives down industrial demand for silver and platinum. Since currently over half of all silver goes into industrial applications and less than 5% goes into coin manufacturing, what do you think that would do to the price of silver?
On the other hand, there is no inherent value to gold. The industrial use, besides jewelery is under 20%. Most goes to coins. So if the economy tanks, what you have is a bunch of rich people and banks liquidating gold to pay the bills at the same time and you watch the value of gold plummet with no real bottom. At least with silver and platinum you have a bottom because of a) the face value of silver (assuming you're buying junk silver), and b) industrial demand.
There have been many who've said that gold has no inherent value and that gold is the ultimate bubble. That bubble has now been in place for 4000 years and counting. I hold some gold and some silver, but no platinum at this point. I wouldn't mind backing out of some of my gold positions because I'm up about 100% since getting in two years ago and I think my money would be better invested in something with a more continuous ROI, like a solar array or wood burning stove. I guess I'd rather invest in something that I'm absolutely assured of an ROI, like productive land, something that helps me with energy or food self-sufficiency, or serves to eliminate my final debt (mortgage) than something that went down right with the stock market in October-November 2008 (look at the charts, it's disturbing).
Will I always hold some PMs? Yes, but they aren't the one best answer to all wealth preservation. I think the best tool for wealth preservation is a very diverse portfolio and skill set. I suspect you're in a good position skill set-wise in a post-SHTF scenario (your skillset will always be in demand), but will you always have access to the tools and resources to practice your trade? Are their things you could invest in today that would put you in a better position to ply your trade even if the systems of support broke down? Off topic, but something to think about.