The poem is full of irony from the start. Its premise (conceit) is inherently ironic in various ways: even if "Life" were a product, there would be no way to stand back and review it objectively (the review itself would be part of life), no basis of comparison (we don't know what death is like), etc. It's also impossible to review life with any confidence before it's over—say, if you have "about half" your life "left," as the speaker does (line 11). Life encompasses everything, so the nature of the "product" can change radically from moment to moment.
The poem builds on these underlying ironies throughout. For example, the comment in lines 17-18—"I'm not sure such a thing / should be put in the way of children"—is ironic because children, by virtue of being alive, have already been exposed to life. At the same time, this comment hints at the more familiar, straightforward idea that having kids (bringing new people into a world full of suffering) is morally complicated.
In lines 20-21, the speaker suggests that the "maker" of life (implicitly, God) might be manufacturing their "product" solely in order to keep a "job." This conception of God as needy and insecure ironically conflicts with common religious depictions of God as powerful, loving, etc.
Some of the poem's clearest ironies come when the speaker minimizes life's importance. They ask rhetorically, "[D]o we need it now?" and call life "a small thing" that "we should take [...] for granted." Their jadedness is ironic in that living people can't possibly have priorities above or beyond life itself. The speaker also clearly sweats small things, like being called "the respondent" (lines 27-29), so they're not quite as above-it-all as they think. However, these ironic opinions mirror, in exaggerated form, common philosophical doubts about life's ultimate significance.
In the final lines, the consumer decides to hold off on giving life their highest rating until they've tried "the competitive product." Again, the irony is blatant: this "competitive product" must be death, and you can't rate anything from beyond the grave! (Also, even if you're somehow able to experience death and decide you dislike it, there's no way to switch back to life.) The speaker ironically treats life and death as if they're competing brands of soap—two consumer options to waver back and forth between—rather than profound, all-encompassing states.