A trans brake shouldn't be one of your first mods, but if you are planning to do a valve body then it's better to get it now. Nobody says you have to use it. Using a trans brake is very hard on the trans and converter. Proper trans cooling and knowing when to activate and release the brake are very important too. I run them on a lot of daily driven turbo cars, simply because that was what it takes to spool em up leaving the line. They are great for cars with slicks , ET streets (tires that like to be shocked leaving the line)
I like the lentech valve body and their converters. Nice stuff.