Coming back to you here G-Nineteen;
Mechanically and functionally, it operates like your familiar Glocks. With the lower receiver/frame corrected attached to the carbine upper, it locks on with a click that is tight with zero slop anywhere. On my G20 / 10mm, the only observation in that category I've noted is the feel of the trigger is a smidge heavier than my Glock (with a 3.5lb connector). I'm really a fan of the concept of this accessory, it's a terrific "accessory" for any Glock owner interested in a Glock carbine.
As to your reliability question, frankly I've too few rounds through mine to report anything definitively as I got it a little more than a month ago. Time of year has made it difficult to get out and shoot it much, so I've not many rounds through it as of yet. That being said, hasn't stumbled once...
Legality in TX? Can't imagine why it wouldn't...here in Kaliforistan, semi-auto carbines must be equipped with the PITA bullet-button type mag release.