I used Mederma, which is some kind of onion extract, on mine right after my pregnancy, so when the stretch marks were very new. I guess I can't say for sure because I did not leave a control area, but it seems that I got some modest results from it. A year later, they have no difference in color from the rest of my skin, but the texture is most certainly still different. If the stretch marks are old, I probably wouldn't bother.
I use Retin-A micro for acne, which along with washing my face once a day and using a fragrance-free facial lotion has really helped. I recommend talking to a dermatologist first before anything, especially before taking advice from me. But by my understanding it involves high doses of vitamin A to push impurities out of your skin and only a small amount should be used a day. As far as skin damage, the vitamin A only goes so far in reversing it. After using Retin-A for over a year I'm only slightly noticing minor acne scarring diminish. A lot of companies enjoy marketing products with vitamin A with the claims that it reverses damage and wrinkles, but I feel that it's only a preventative treatment for the most part. So I'm not sure how this would help with stretch marks.
Also, I feel I should note that Retin-A reduces your resistance to UV, and my dermatologist recommended that I use spf every day on my face. And using spf has become a debated topic as of late.