If Springfield "advertises" that they will refinish earlier XDs that have rusted, they would have virtually every XD made sent to them for "free" refinishing.
The facts are:
Only a few people have reported some evidence of rust on the earlier XDs. It just seems like a universal problem because of the way the Internet works (you know, one person says something and 500 other people repeat it within 24 hours which then repeats exponentionally).
The way you read some of these "rust reports", you'd think that the pre-Melonite finish actually caused rusting, which of course, it didn't. Anyone familiar with guns knows that if you maintain a finish of ANY kind and keep it lubricated, it won't rust. What that means, and this has been stated by Springfield, is that the incidence of rust on early XDs is low enough to suggest that owner maintenance (i.e., lack of) is the cause of the rust rather than it being a finish problem.
People who buy pistols with these "wonder finishes" seem to think that you never have to touch them with an oily cloth again, nor oil in places where you would otherwise ALWAYS oil on blued guns.
With that said, it IS accepted that the Melonite finish used now that replaced the earlier type finish is a more durable finish. The Melonite is identical (not similar, but identical) to what is also known as "Tennifer" used on other pistol brands.
What applies to your case is that ALL of the XDs made during April '06 and after have been manufactured with the newer Melonite finish.
What that means to you is that if you are buying a new pistol in the next few weeks, it will almost for certain be a Melonite finished pistol unless it's sat at the dealer for MANY months.
I bought my XD9SubCompact on July 4th of this year. I was curious myself which finish it had so I contacted Springfield with my serial number and they told me that mine was manufactured WITH the Melonite finish during the later part of the month (April) in which they began using it.
If you are buying a used XD9SubC, I doubt if Springfield would warranty it since most warrantees aren't transferable to subsequent owners. However, if the price is right, you would be better off sending it off for a Diamond Kote finish which is far superior to what Springfield would do to it anyway.
Pistols sent back to Springfield CANNOT be finished in Melonite because that "process" MUST be done at the time of manufacture.
Carter