I haven't tried that company's shirt, but I did wear a Terry jersey with SPF two weekends ago. It was 85 F, I was out in the sun for 4+ hours and for once, I had no extra lines where my sports bra ended (under my jersey). It really, really worked! (I thought the tag said SPF 50, but Terry's site doesn't list a rating for the newer versions of the same jersey...it just says MYN(R) UV protection).

It looks like quite a few of their jerseys have this and I can vouch that it works!