before sales service availability of advertised products after sales service speed of shipping (but bear in mind that postal service delivery standards are outside a vendor’s control) were the vendor's claims delivered?
unique/unusual aspects of the carrier the quality of the product quality of instructions comfort, fit, adjustability ease of getting baby in and out learning curve applications the carrier is best suited to/not suited to are the manufacturer's claims borne out age/size of your baby; would the carrier suit other ages/sizes? best/worst features
have actually used the product or dealt with the vendor as a customer, offer a fair and honest review, and don't compare their product or business specifically to your own.