When I first started assembling my lab, the sales people from several big companies swooped in with their offers. One of my first blog posts was about that. It was an odd experience. But in the end I did the majority of my purchasing through a local distributor because he had a wider selection than any one company and he took the time to work with me rather than just throw fliers at me. And not only is he the sales and delivery guy, but he's sleeping with the company owner - his wife. I can also call him personally at any time to ask him a question about a product or have him send me a quote. I'm a personal attention whore like that.
But never has the customer service been more useful than this semester. On at least two occasions I have had to talk to him and ask for a product for me teaching lab, because I'm woefully under-prepared for yet another lab. On a day's notice he has sent me products critical for the lab with no PO, no payment and nothing other than my word that I will fill out the paperwork and get them paid. Now obviously I'm not going to run off with my $80 worth of supplies and disappear, but try calling Sigma and getting anything from them without some sort of documenting paperwork. Maybe large accounts can do that kind of shit, but I'm not in that position. It's nice to have that kind of resource if you need it.