Logo ware is really can go both ways. I see people wearing Google T shirts all the time, and sometimes I think it does more harm than good. I mean, you get some nasty slob wearing your T shirt and that ain't good.
But if you are just referring to you wearing the logo wares yourself, that's all good, if it's done in good taste and style. T-shirts, jackets, mugs, your logo on your vehicle, pens - it's all advertising, and possibly lead-generating. But the question is, does it generate more leads per dollar than other forms of advertising, like PPC.