Planet13 - 3:19 pm on May 25, 2011 (gmt 0)
I don't have any proof one way or the other about link exchanges.
Although I can say that many of the top ten sites that are in the niche I follow closely seem to rely on link exchanges, as well as some free / low cost directories, some spammy article links, and a few others. They don't have a lot of natural links.
Those are all ecommerce sites too.
You might try a small amount of link exchanges with very closely related sites.
If I were going to do a link exchange, I think I might look into exchanging links with established sites that sell the same thing you do, but sell to different countries. For instance, some of the items I sell I am not (due to licensing restrictions) able to sell in Canada. So I am looking for Canadian companies that sell the same thing and are not able to sell in the US. I'll see about swapping links with them.
In the end, I think that you should have some non-ecommerce material that you should use for getting one-way links to.