As a reseller, I'll give the client the following:
You can have it:
1. Fast
2. Cheap
3. Good
You can have any two of the above at the same time. End of story.
Being the fastest out there is grand, but you need to be aware that this makes you the last resort for most people. As in: "I fucked up (which means I'm probably not very good at what I'm doing), so now I'm going to go with someone that will deliver in time despite the fact that I've not left enough time for the job to be done right. Then I'll blame the supplier for the inevitable cock up!"
I would insert an evil laugh here, but it seems redundant.
In my experience, 90% of people looking for next day are problem clients. The other 10% are good eggs in a bind, but you'll know who they are already. There's no need to offer next day if your competitors aren't, just go for good prices, quality and customer service.