Is this rude?

It's not rude, it's dishonest.

If you're only willing to buy used gear via private sale, you must also be willing to take the risks associated with buying used. If you're not willing to take the risks, don't buy used gear.

Go in , get your demo , get the salesmans card, a week later , send him a note that you decided to go in another direction, but you appreciate his time , and send him a check for a nominal amount, say 25.00. and if you find the shop to be friendly and helpful, try to use them for future considerations.

Thanks for the candid responses, everyone. It's nice to hear the opinions of those who are far more experienced than I.

Try this,lay all your cards on the table and in the end retail joint "may" cut a deal that's a tempting 1/2 step towards you.If they do quote a discount to rescue the sale,you can weight the better route ,keeping in mind all the pitfalls of doing business via mail. Shipping damage, shady sellers,miscommunication,misrepresented or abused items. Add up all the charges ,pay-pal,shipping,handling ect.
I have done it both ways and much prefer to see, touch and hear my potential new gear.Imagine the anxiety during the period of time between transaction to confirmation. You will experience if you go mailorder. Along with the extra uncertainy if deal goes south. Rude or not is beside the point really that's your call and cross to bear in the end.
Just think it through carefully because as the purchase price goes higher so does your personal investment,which is not all money but time as well.Time is most valuable.
Personally I enjoy the shopping ,looking,hearing the sales-persons input,and knowing I have the power to say lets do this deal and seeing the process of said sale go down.It's like a dance,a sales "Tango" if you will and can be much more fulfilling then the:is it going to get here in one piece,is it like they said,is it a cinderblock in a box?

It seems like people are more wary than I thought about buying off audiogon. I've had my problems with eBay, but I thought Audiogon was generally a different story. Was I wrong?