I agree this can be a good deal. However, to use it just to get discounts can be sketchy.

I own a business and actually am affliated with TPI (mentioned in an above post). However, I also spent a short time as a travel agent so I know the ends and outs of using the affiliation.

First of all, if you use it correctly, you can not only get great hotel rates, but airfare, Eurail and auto discounts as well.

For instance, when you become an agent, you are able to use consolidators to buy your tickets. This can come in handy as it will allow you to obtain tickets overseas (no domestic) at low rates. The tickets you buy from consolidators online are marked up, having an IATA number allows you to buy a ticket at the much lower rate.

For example, if you want to go to London from Seattle, you might get a quote online or from published air of $750. A consolidator will sell that ticket to the travel agent for about $500. The savings can be quite substantial.
I do alot of travel overseas and run a business where getting tickets for my clients at a reduced rate matter. I also buy tickets for others and add a commission. I can make $100-$200 off of every ticket.

Once you have been with an agency for a year (sometimes less than a year) you are able to recieve travel agent discounts with major airlines like BMI, British Air, SAS and Virgin. I think last year Virgin offered a travel agent discount in economy for $199. They also have discounts for PE and UC. All of the airlines I mentioned except SAS require an IATAN card. Those are hard to get. However, when you hook with with a good agency, you will be issued a temp card after you have been with them for 6 months. The card is good for 6 months. The idea is to be a real agent. To truly sell and to truly try to make money. Some airlines (domestic ones as well) will allow you to travel with a CLIA card. The CLIA card does not have the commission restrictions that the IATAN card has. It is hard to keep an IATAN card if you are not truly trying to make money. You must make $5000 in comission to keep it.
It's hard.

As far as hotels, some hotels do requrie to see some sort of travel agent ID. The Starwood chain almost always asks to see my card. They are times when it is not asked for and there are times when they make a copy of it.
When I travel overseas, they never ask for it. I consistanly get a 50 Pound rate at several 4-star properties in London. When I travel next week, I have a 40 Euro rate in Budapest at the Ramada.

I guess what I am saying is that if you use this perk to its fullest, you can make some money as well as save some money. But make sure you have a great host agency. One that is really a travel agency and not a smaller one just looking to make money off of you.