Anyone used this? Would you recommend it? Better yet, has anyone used and can recommend some of the cheaper alternative adhesive underlays?
You can lay an engineered board as a floating floor this has been the preferred method of installation for many years, you would need to make sure the floor is flat before you start using a long straight edge. When laying the floor you would glue the joints using a D3PVA glue, a standard wood glue will create noise when walking on it and become detached with movement.
Glue the joints and strap the first 3 rows together until they set, then it makes it easier for the rest of the floor laying, be mindful of your expansion gaps. Make sure that the engineered board is up to room temperature before you start, I have seen many DIY projects where it has been laid in the cold,, It is not a pretty site.
You can use a Polyethylene thermal underlay which is more cost effective,, a 6mm variant is here
http://www.allbriteuk.co.uk/thermall-6mm-underfloor-heating-insulation-coverage-10m2.html
We have used this for over 14 years with engineered board and laminate flooring without issues.
Acoustic values are also good reducing impact noise by 21db