SMS works flawlessly - no issues there.
MMS (Photos) really don't work consistently - though I haven't charted the details - but let me summarize the issues.
I'm using a stock Moto X, running the latest version of Hangouts.
Switch to Option 2 and use my Google Voice number and EVERYTHING works *PERFECT*.
Now that all the other carriers are supporting MMS/Images via Google Voice, it is a GREAT opportunity for Sprint to showcase this messaging opportunity for all of it's customers.