I needed a roomy vehicle to accommodate our new baby (and all the stuff that comes along too) as well as provide good gas mileage for commuting 60 miles per day for work. Seeing as a manual transmission is almost a requirement for me, my choices were limited. I compared the Mazda5 to a few mid-size sedans and found that none could compare in terms of space or price. My wife, who always swore she would never drive a minivan, loves it so much that she now wants to learn how to drive a manual so that she can drive my car instead of her CR-V. Our baby loves it too :) The 5 is so fun to drive that I feel like I'm driving a sporty car, not a Micro-Van - great mix of fun and practicality.
Availability of a manual transmission (a must for me). Gas mileage. Averaging 28 in 80% hwy, 20% city. Sliding doors - very easy to get baby in/out of vehicle and good for tight parking situations. Under-seat storage. Sporty ride/handling. Standard features for the money.
6th gear for manual transmission - seems to rev a little high above 65 mph. Maybe the availability of AWD. I think my wife would replace her CR-V in a minute if she could get a Mazda5 with AWD.