If it's safe to use steam or not is a controversial subject. I've done it, and can attest to it's effectiveness. In general however, it's not a good idea to heat the vinyl, but the steam is actually not that hot. As shown in the video, it doesn't scald the record....but it will warp it slightly during the process. The warp is temporary, and in some instances I've noticed the treatment will relax the vinyl, helping to flatten any existing warps.
With all that, I currently only use steam to warm the cleaning agents I apply to the grooves. My philosophy is that cleaning records - with all it's obvious benefits - will also wear the vinyl as assuredly as playing it. Consequently, I do as little as possible to achieve the desired result.
How boring it would be, this endeavor
If all we heard was "perfect sound forever"