I though that latest version should support older one, but I'm still having some problems with piece of code written with Access 2007 and trying to run it on Access 2010... so if I spoke by personal experience I'd say "no it won't work" or at least "be careful".
It was an A97 mdb opened in 2010 and converted to accdb, so no new features. When trying to open in 2007 it just says it's not able to open it (can't remember the exact msg and the guys 'puter that it's on isn't here ATM). 2010 dosen't seem to have any 'Save as 2007' functionality unless it hidden somewhere I can't find.
probably best ignore me.. just found another thread on this issue and maybe the fact that I converted the A97 db into accdb rather than import the objects might be the issue... can't test it at the moment, will have to wait a few days
Actually MVF were introduced in 2007 so that's not an issue. But your point in general still stands - one has to watch out for new features such as web browser control & navigation control, shared gallery and then few more.
Also note that it's not also always a simple matter of "not using any 2010 features" - there are several actions that may cause 2010-only features get added, a good example being the new MSysResources table. FMS has an article about this particular scenario.
I'm of opinion that you are far better off picking one or other. Remember both offer free runtime that everyone can download and use so you only need to pick one to develop with, and give your users the matching version runtime + your application + a handy shortcut and you've saved yourself a big headaches with handling differences between versions.