I bought an Innova inflatable 2person kayak last year because (1) my fiancee wanted to go boating with me occasionally and (2) because they hold more gear!
We've had quite a few fun trips on local lakes.
She still enjoys the occasional trip and seems to like the two-person idea better than having her own because she can kick back and enjoy the ride if she feels lazy
One un-fun part is getting your SO to try to synchronize her paddling stroke with yours (or vice versa). The other is balance - one leans and both could be swimming!
If I were to go with a hardshell kayak, i'd consider the Loon 138T. I just checked it out at REI and was really impressed.