Running SharePoint 2013 in 2010 mode limitations

Planning on moving to SharePoint 2013 but 75% of the IEs here are still version 7, since SharePoint 2013 does not support IE 7, am planning to run the Site Collections in 2010 mode but not sure if there are any limitations with 2010 mode (may not care so much about 2013 features at this point).

our SP2010 environment currently has one custom application and the farm is limited to few users. however we are planing on exposing it to all users and have some custom apps on it in few days. I tried testing my existing custom app in sp2013 and it wasn't fun at all. so am tring to move all new apps to Sp2013 so that i don't have to deal with ugly migrations.

any ideas? also will the bits change in the final release of the product?

Thanks! 

Alert from TechNet Posting