“The Steam refund offer, within two weeks of purchase and with less than two hours of playtime, applies to games and software applications on the Steam store.”
There are separate rules for in game purchases.
In game purchases that are consumable in any form will not come under refunds and Valve claims that the DLC pages will specify the refund policy.
This is a welcome change but I’m concerned about people abusing this system.
Valve does claim to track abuse and stop offering refunds to abusers.
One thing to note is refunding a game prior to a sale to buy it on sale will not be counted as abuse.
The full details for Steam Refunds are available here.