Depends on the type of hotel, but yes, at a 4 or 5 star property I think it can work in your favour, all other things being equal.
People in an upscale establishment are often proud to be working there, I mean this in a good way, i.e. not the "snooty" factor, simply stating that it is harder to get hired at a Peninsula hotel than say a Double tree or similar, hence people take a certain pride in their job.
By not showing up dressed like I just stepped off the beach or came from the Nascar track, I show that I have some respect for that. Of course there is no need for a suit and tie, but, IMHO, paying a little attention to what you wear is always important.
All the above IMHO only, some people are addicted to the jeans and shorts look, and as they "paid for their room/ticket, can wear what they want....etc.." they are perfectly welcome to stick to it...

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[This message has been edited by JohnG (edited Dec 22, 2003).]