Define "slimy". Offering someone something which you have a very good reason to think they'd want seems like about the best that marketing can ever be.
There's lots of slimy marketing tactics. Here's one.
Give someone something for free, without telling them its a trial, then have it break down in some predictable manner shortly, then sell them something very expensive to fix it.
Example. You buy a printer for really cheap, you're happy with your purchase, you print off some pages and then after the 8th page, your printer runs out of ink. You go back to the store to see ink for your printer is exorbitantly marked up.
That is a slimy marketing tactic. It relies on common weaknesses in reasoning we humans have, in this case, a sunk cost. You've invested time and money badly, and you are unwilling to see what lies ahead as a worse option as backing out and getting something else.
Can you see parallels with this tactic in what steam is doing?