They never really release a steam machine the first time. They were all windows PC's that had decent specs for the footprint that the things were, and ran steam in big picture mode. The experience wasn't bad but it didn't give you anything a "non-steam machine" gaming PC that you could build yourself didn't give you at the time, and building a PC yourself was both affordable and very much could provide a better product/experience.

I think it's unfair to say they flopped the first time when it came down to PC vendors not really shipping them with steam OS because at the time it was not ready yet. It's fairer to say steam OS flopped back then and the hardware didn't sell as well as it could have as a result of them being sold almost entirely as windows PC's.

At the time I fully remember (because I bought an Alienware Alpha for like $350) that there was supposed to be an option to buy a steam OS variant that never really materialized. Never saw it anywhere but in press articles and reviews.

I had the windows variant. There were some drawbacks: had to provide my own keyboard and mouse), the controller that came with mine was one of the old school XBOX 360 controllers, windows 8, and big picture mode sometimes not allowing me to leave it to return to the desktop. But all in all my experience with it was pretty good. Certainly comparable to the gaming PC I had built and owned before it (in that it ran the games I wanted to play, which were games of that time period at a decent frame rate and quality).