Yes. Those who haven't received a Google Voice invite for starters. Also, GV texts come through to the recipient as your GV number which is out of network and my wife and I don't have Friends and Family either because we can keep our bill lower by staying on our older plan + texting than "upgrading" to a newer plan that includes F&F. So, since 90% of my texts are to my wife, it makes sense in my case and those like me.
If you both have smartphones, then you both need to have data plans, which would give you free use of the google voice app, right? I don't see what F&F has to do with it, since it's only for calls, not texts.
Or maybe you have a smartphone and your wife a dumbphone, in which case you each would need to have a $10 texting plan to get in-network texting. Then wouldn't it be better to use google voice for unlimited texts, and get your wife a $20 texting plan? Of course, you would have the inconvenience two phone numbers; one for texting and another for in-network calling.
Maybe I'm missing something, but aside from the inconvenience of a separate number for in-network calling, I don't see any scenario where you would need a texting plan on a smartphone, unless you have 2+ dumbphones on the family plan and pay the $30 to cover texting for everyone.
I have 5 phones on a family plan with F&F, and everyone has a google voice number on the 10-number list. This effectively gives everyone unlimited incoming calls. Outgoing calls are also unlimited, by placing the call using the google voice number (a simple one-tap option on the Droid). We only use the cell number when calling other friends on Verizon, so they don't have to use their plan minutes.
Really the only inconvenience is that we lose incoming caller-ID (the google voice number needs to be displayed in order to fall under the F&F free minutes). GV can present the caller before you answer, though.