I recall seeing a thread on here a while ago from a fellow artist who printed some cards for herself at Target and was extremely unhappy. I think the main thing to be aware of is that Target add a white border around the cards when they print them, which suits some designs better than others.
 
I believe that thread was within the last year, so hopefully if you search the forum you will be able to find it.

If you click on the link labeled "In-Store Pickup at" Target on the home page it will take you to a new window that clearly defines the differences between the two printing. Target utilizes Kodak which places a border around all the cards. Not all Target stores offer the printing services. I'd double check to see if there is a store locally - or have your client do this. It seems like everyone has had different experiences. It totally depends on the store.  In my experience I had to go to a suburban store a few cities away. The printing department didn't even open until noon on a weekday. In fact, the printing department at this particular store was neglected. The printing equipment needed cleaned and the staff needed training. In my case it's just not that convenient. I will also add that it was a couple of years ago.  
 
I would really double check to see if there is a local store with convenient printing hours as it is different from the main store's hours.

I have often noticed that I'll make one sale to a customer who has the card printed at Target. Then an hour or so later, I get another Artists Services email that informs me that a bulk order of that same card was purchased and then printed at the same Target. I can only conclude that some customers, before they have Target print their cards, will do a test printing. The printer can then adjust and calibrate the card accordingly. It may be a lot of hassle for a customer to purchase cards in 2 stages, like this, but it is a wise choice when the Target printing is so inconsistent.

Thanks for sharing your experiences.  I passed it on to the client.

You are all correct, the quality of service at each Target location varies greatly.  GCU is quick to take locations offline or walk photo lab staff through simple remedies and push reorders through all in an effort to satisfy customers.  Unfortunately the photo lab departments have a high turnover.
 
Lisa, you experienced a common problem with the scoring and falling apart.  Some photo labs will mistakenly use perforated card stock.  We are however seeing this less frequently.
 
When a shopper has the time or is willing to pay a little extra for expedited shipping GCU always recommends ordering directly from GCU for a premium product.
 
As best we can, the in-store pickup orders are shepherded to result in a satisfied customer.
 
But for a same day, custom card pickup it is still an excellent option.