I have some personal qualms about supporting “the biggest fish” in the pond, since that tends to lead to the Apples, the Googles, and the Microsofts.
However, Steam hasn’t particularly abused its market power, and has even used it to create a very successful Linux handheld that has both helped propel Linux desktop adoption and added upstream improvements to Linux in general.
I’ll revise my opinion when Valve changes to a more overtly predatory model of capitalism, but for now, I’ll enjoy only needing to keep a partial eye open.