I chose Televue largely because of their reputation for excellence. But the product description was also critical. Televue advertises that their 2X and 3X barlows are corrected for scopes down to F/4, and I can vouch for that as my reflector is an F/4. Being able to use my 32mm eyepiece with the Televue barlow was also a slight consideration since most barlows are designed to work with eyepieces 26mm and shorter.
I have been very pleased with the performance of my Televue barlow. I have not noticed any visual distortions when using the barlow, not even at the edge of the field of view. I was able to find the central star in M57 using the barlow to reach 200X. Also at 200X, M13 filled my field of view and I was able to distinguish between blue and white stars with my 8†reflector. Overall, images were crisp, and I have not noticed any differences in image quality when viewing with just my Meade Series 4000 Super Plossls or when using my barlow in conjunction with these same eyepieces.
In addition, I am impressed with the sturdy construction of the Televue barlow. The strong metal tube has no problems supporting my 1-pound Vixen Superwide eyepiece. And the compression ring holds my eyepieces very firmly without leaving set screw marks.
The only concern one might have about purchasing a Televue Barlow is that it does require a bit of back travel with my telescope. This is no problem for my three inches of focus travel. However, I would recommend testing it out first at a star party before purchasing it for use with a 1†or 1.5†focus travel focuser.