Yep. Range is definitely decreased, but within the actual city, can't tell the difference at all on FM.
This:
http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=241/prd241.htm
Has been on my to do list forever, just so low down on the priority list that I don't really care.
Meme....would this just plug into the back of the stock radio? I'm assuming you unplug the stock antenna.