Jennifer,
We have separate records for spouses when the spouse either contributes on her own (and wants it recorded that way) or when the spouse has positions within the organization that are different from the other person. We tie them in the Realtionship" but also give them the same constituent ID but with a special prefix.
I've only been with my organization about a year. When I arrived the database was full of spouses. These individuals were given their own records only if the checks were signed by the spouse. We address all correspondence and donor "honor roll" lists to both of the individuals, so having two records can sometimes be redundant. But the automatic soft credit is the best way to go. Soft credit for the full amount to the spouse and then when you run exports make sure to only use the "head of household" or the "first constituent found." That way you're not getting any duplicate numbers.
I just read about a group that uses the constituency code of Spouse of Alum which I think would help us greatly - as we could get those numbers to pull in with our regular Alum & Non-Degreed Alums on financial reports. For us that's the largest problem right now - as Spouses are pulled as "Friends" on our code tables into reports.
I'm unsure if you need to have a second record if the spouse is the one that signs the check - auditing purposes and such.