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We sure do! The code is SMX14MOZ. Thanks for asking!

The Matt Cutts stated that href-lang is important because it will help Google bot know that the page is intended for a different language, rather than a poorly translated page 'written' just to 'rank'. If it seems like everything is okay, then err on the side of caution and use href-lang. You may just see an improvement. However, the critical piece is making sure the pages are well written/translated for their intended target. Perhaps search engines have gotten better at weeding out/penalizing poor translations, but I would use href-lang just so I could sleep at night. At least you'll know you did that much. If you really want to go for the gold, get someone fluent in the target languages and see what they think. You may end up with some edits. There are a ton of Spanish dialects and what reads well in Mexico might not read so well in Spain.

For one, the hreflang markup tells Google which pages are similar to this exact page in your other localizations, which is not specified at all in webmaster tools.  From my understanding, the hreflang tags will swap out a page to the correct localized version on search result pages, which is doing a lot more than simply telling Google that the content in a subfolder is localized to a specific location.

Thank you for these answers. They provide a lot of insight. One comment about the translations though, is that there could be different countries using the same language (English is the obvious example here). While we can identify the pages through the use of different country subdomains, each country would still want to publish content on their own sites.