The Tru Center I had would not lock down at all. The blade screws just would not keep enough tension on the blade. The blade would float and dig in to the shaft.
In fairness to the Tru Center, I purchased mine around 10 years ago. I don't know if they've made any changes to it since then, but if not, I wouldn't buy one.
What Bob says above is correct, even with the pencil type. You can correct it though with experience and some good sandpaper. Just takes some work.
I use a Woodchuck and would recommend it to anyone. You can get the same job done with a jig and any belt or disc sander, but I like the all-in-one portability of the Woodchuck.