This is probably the best plugin for fast theme customization out there so I feel kinda guilty for starting off with a "Please make it better" post.
This is not a bug I found but a slightly dangerous situation I've discovered while working on a client site with Option Tree and WPML.
I'm using page and categories selects to choose which content to display on the front page of the site.
What WMPL allows me to do is to change the display language of the WordPress admin area and that's where the trouble is.
If I have a page or category selected on Option Tree in another language than the admin area is currently displaying the Option Tree selects display the pages available in the display language and doesn't recognize a translation of the selected page.
I have the english page "E_frontpage" selected in Option Tree.
If I open Option Tree while viewing the admin area in french I only see the french list of pages and Option Tree doesn't know that "F_frontpage" is the translation of "E_frontpage".
If you then press Save Changes for some reasons, all the language dependant selections go back to being unselected.
I have twice now accidentally wiped out the customers frontpage by not realizing this. It's not a catastophic thing to repair but it makes me uneasy delivering the page into the hands of someone less knowledgable.
I'm guessing that this is also a problem for pages and category checkboxes as well as the taxonomy and custom post types options.
a) If WPML is detected, show only default language
b) Use WMPL api to detect the translations ID based on display language
I would be happy to help with testing this if you're interested in making this a feature.