I have had my Phantom 2 Vision + for a couple of months, but I haven't yet ventured into the more advanced functions. I am relatively comfortable in Phantom mode, although I do sometimes worry about crashing (haven't crashed yet.) Sometimes my quad will lose its satellite lock temporarily, which is always concerning when it happens, but it's always temporary and hasn't yet caused any problems.  
I would like to use the Course Lock and Home Lock functions, which I believe requires switching to Naza-M mode.  In the software, when trying to switch to Naza-M, there are repeated warnings about needing to be an experienced user.

If I understand correctly (and I'm not sure that I do), you can fly in GPS mode while the quad is in Naza-m mode.  If I do this, isn't that basically the same as Phantom mode, with the added functionality of the IOC?  Are there any other important differences that I need to be aware of?  If I do this, and the quad loses its connection to the remote, will the quad return home as is does in Phantom mode?  

I realize that these may be basic questions for experienced users, but the documentation with the drone really doesn't give very detailed information about these issues.  I appreciate any help.  Thanks!

GPS flies the same in Phantom and MazaM.
Just proceed with caution as you learn the NazaM features.
You'd be well advised to study up on Course Lock & Home Lock so that you know what to expect.

Here is a great video on the subject.

You got it! Can't imagine my Phantom without IOC. My recommendation, just be sure to set S1 down position to FAILSAFE and not MANUAL.

Having HOME LOCK is such a great feature. And using rudder while flying in a straight line using COURSE or HOME LOCK makes the unit spin on it's axis, while flying in straight line. This looks so incredibly cool. haha

Only problem I have run in to in NAZA-M mode is getting S2 to reset home position by toggling it. I never had issues with hits before I switched to NAZA-M mode. Now it is hit or miss whether I can successfully reset home position. There is a thread on this topic and we are working through it, but something is up. for sure.

Other than that, IOC is awesome and amazing. Best of luck!

And yes, even in NAZA-M mode, both S1 and S2 up position is the exact same GPS mode as it was before making the switch to NAZA-M.

Here is a good video explaining NAZA mode. Just STAY AWAY from MANUAL MODE in setting up your S1 switch. Personally I would go with FAILSAFE. http://youtu.be/Prs7txS_NDA

just carefull with manual mode, i crashed mine  after switching the mode to NAZA

josephbobowicz@ Posted at 2014-10-5 00:48
Here is a good video explaining NAZA mode. Just STAY AWAY from MANUAL MODE in setting up your S1 swi ...

Very well done video. A+

stryjek Posted at 2014-10-5 01:15
just carefull with manual mode, i crashed mine  after switching the mode to NAZA

Agreed totally. Bad idea to leave the bottom setting of S1 as Manual, jun my opinion. Unless you really know what you're doing. Set it to FAILSAFE. I have S1 set as OFF, ATTI, FAILSAFE. Works great in my opinion.