Of course, we it helps support our development efforts when people buy Weaver Xtreme Plus, but we really do recommend that you try the free version first. It is really full featured.
Plus makes it easier to customize some things, especially with Fonts. But the Free version has many of the Plus options displayed, but grayed out, so you can see if those options do things that you need to do.
But any efforts you put into designing with the free version will carry over 100% if you decide Xtreme Plus can help make your designing easier.