Straights and big trucks won't benefit much from it, since most of the time when they fill up they will be getting enough fuel for a 7-day shower.
As for vans, the Expedite King program is certainly better than the programs for vans at the Pilot, Loves, Petro, you name it, and it's better than what the TA had for vans previously. Like xiggi said, tho, it really wasn't well thought out. The sticking point is that you are required to buy food in order to obtain the shower. That turns many off, not because they don't want to buy food there, but because it's a measure specifically designed to ensure that they buy food. If the TA gave me a free shower for 15 or 20 gallons fuel, you betcha I'd be buying food and stuff from the convenience store a lot more often than I do. But requiring me to do so, and then try to keep up with with purchases in the last 24 hours and then the 3-day expiration of the shower, it's more than I want to deal with in most instances. KISS.
Having said that, if you're going to eat anyway, and you get 20 gallons of fuel, there's a free shower. If you shower at the J you're still likely going to eat something, so in order to get a free shower at the J you must get at least 15 gallons, twice. It's only a single 20 gallon fill-up at the TA, provided you also buy a meal sometime within 24 hours.
Using simple math, at $3 a gallon (which it is in Utah for some silly reason), you need 30 gallons for $90 at the J to get a free shower. At the TA it's 20 gallons for $60, plus a $10 meal, so you get a free shower for $70 spent. So at the TA you get a free shower for only a single fill-up, and you're likely going to eat something whether you fill up at the TA or the J, so really the TA is a better deal (except that the J gives you 2 towels instead of 1, which is the deal breaker for me). OK, fuel is a little cheaper at the J than the TA, but like I said, I'm using simple math here. If you use a Comdata card at the TA and are with a carrier that gets you additional discounts, some of them significant, then the TA becomes an even better deal.
So the Expedite King program isn't the greatest, but it's better than what they had before, and they didn't have to do it at all. For that I'm grateful.