SQlite3 works great in 64 bit mode.

You can find our own 3.7.16 version of the SQlite3 external library, to be used in 64 bit mode, from SQLite3-64.7z, since there is no official Win64 library released yet in http://sqlite.org
No problem so far, and pretty good performance.
Jut a weird bug about SQLITE_TRANSIENT constant, which should be pointer(integer(-1)) instead of pointer(-1) when working with virtual tables columns - but nothing to care of in your user code, since the framework will handle it for you.

I suspect some part of official System.RTTI.pas unit as provided in XE2/XE3 is broken in Win64.
For instance, I think it does not handle a method returning a string.
Our mORMot.pas implementation has been tested with the same regression code as in 32 bit mode.

Your own tests and feedback are welcome!
Feedback and detailed tests results are available in our forum!