I definitely pay attention to them. I feel like certain voices compliment certain looks better, so I spend as much time as I have to to get it right. I also avoid pairing up my sims with a mate who sounds exactly like a family member, because that's just weird. I can't tell you how many times I've had a sim looking for love at a bar or at the romance festival and just when I thought I've found a suitable townie for him it turns out she's basically his mom in a different body.