Some do swear by glides, others have had them and reverted back to glideless.
I have a powerful TM with a 5M blower and 69 HP engine. I have used glides quite extensively but formed the opinion that the cleaning quality and dry times were suffering, as a result. I went back wanding without the glides and things became good again.
I do have a reserve wand fitted with a glide for those rare jobs, especially some rugs, where I dont want as much suction.
Glides do restrict suction through the wand and I am sceptical about claims of improved airflow, they also greatly diminish agitation.
However some wands by their design are difficult to move over the carpet without a glide fitted, the Titanium Wand is a prime example.
The design of this wands manifold which greatly increases suction compared to others, compensates for the restricted airflow/water lift of the glide.
That's the conclusion I have drawn for what it's worth, if I thought differently, I'd still be gliding.
They are a godsend though for lazy carpet cleaners!
Dave.