I am always in search of really good, French croissants, and my standards are high. (See http://chowhound.chow.com/topics/762135 for my detailed list of criteria.) I always try the plain croissants first and pain au chocolat second. Filled croissants, etc., do not really show the quality of the pastry itself.
My main searches have been in Paris, Seattle, Manhattan, and San Francisco, but a recent trip to Tampa gave me a chance to visit two local bakeries. I tried both in the AM, to be sure of getting fresh products.
The first was Amelie's French Bakery & Cafe, 1633 W Snow Ave. (The webite links on Yelp, etc., all point to a similarly named bakery in Charlotte, and I don't have a correct link for the one in Tampa.) The croissant was enjoyable in its own way, though not much like a really good French croissant. Too light and with too little to bite on in the middle. It did not leave me interested in trying a regular pain au chocolat. I did try a twice-baked chocolate croissant. It was very nice, with lots of chocolate, but that left the pastry a bit heavy.
My second try was at l'Eden Restaurant and Bar, also opening early as a cafe and bakery. Both the plain croissant and the pain au chocolat were very good. They had the flakyiness I expect, with a good texture in the middle. They were better than most in the US cities I've visited, and would both be quite respectable in Paris. This latter comment is actually high praise, considering the mediocrity of the average Parisian croissant these days. My one criticism is that they could use a more flavorful butter, although the butter taste was still pretty good.
500 N Tampa St, Tampa, FL 33602