When you use "in" the market, I tend to feel that you are talking about a product or company compared to others in that market.
We need to position our product well in the market.
CompanyX is our most important competitor in this market.
In this market, it is important to be innovative.
You can also be in the market if you are willing to buy something. Compare:
CompanyX is on the market for a takeover.
CompanyX is in the market for a takeover.
The first sentence means someone can buy them - the second indicates they want to buy!
If something is for sale, it is on the market.
Our product has been on the market for two months now.
There is a lot of software on the market.
I want to move to another town; I put my house on the market.
In today's market, it will take a while for my house to be sold.