Hertz has always been pretty good about waving the #1 Gold charge and has let almost everyone become a memeber so not real sure about the 'deal that U is offering.

But more importantly Hertz charges you money to give you those miles (see below from Hertz site):
Frequent Flyer Surcharge
The following applies to reservations booked August 30, 2002 forward for rentals picked up October 1, 2002 forward. For rentals in the U.S., Puerto Rico, and Canada when the renter chooses to receive Frequent Flyer miles or credits from the following U.S. airline programs Hertz will assess a Frequent Flyer Surcharge equivalent to $0.50 per day up to a maximum of $2.00 per rental. The amount assessed is collected by Hertz to offset a portion of Hertz' annual cost of participation in Frequent Flyer programs.
Alaska Airlines
Aloha Airlines
America West Airlines
Continental Airlines
Delta Air Lines
Frontier Airlines
Hawaiian Airlines
Midwest Airlines
Southwest Airlines
United Airlines
US Airways