I apologize for misrepresenting any information regarding the ownership of hotels.com, but the point of my comment here is to answer the question of value for the person that bumped the thread. No need for flaming. I'm just sharing my experience as a gold member with the site, the benefits/value for me isn't astounding.

Most of my bookings with the site are rooms booked in South East Asia, and for cheaper rooms (like vincewy mentioned)- well, there's no need for a discussion here, you pay for what you get. But on our stays at resorts in Phuket that were mid-higher tier hotels, we definitely got the lousiest inventory of the bunch. On stays that averaged $180-250 usd a night, we were always put in the rooms that were the further-est end of the property. We tried requesting for room change that were more accessible to the lobby, but we were always denied by the front desk explaining that rooms are specifically allocated for third party booking sites like hotels.com, so I'm not sure about the site being a massive driver in inventory of rooms. Calling the gold hotline on this one didn't help us either, they will tell us it's beyond their control because it's the hotel that decides where they put you, even when the hotel site still showed inventory of the same types of rooms available online. Maybe it's just bad luck for us, but just merely sharing my experience.

Coupons wise - make sure you try them out before you make flight plans, because often or so - they have location restrictions. Just like the recent ones, I tried applying for bookings in Asia, they came out as error, stating only available in North America. Also, some coupons do not stack with the 10 night stay reward, so always call and check with the site before you make any travel arrangements.

The "free nights" are essentially just a rebate redemption scheme. Based on your the average cost of the last 10 nights you stayed.
So let's say you stayed 5 nights for $50 each night, 5 nights for $100 each night. You get a ($50x5=$250 +$100x5=$500)=$750 / 10= $75 "free night" credit.
So it's not a "free night" per say, but it's just a 10% rebate on your next booking after you complete your 10 nights. Silver or Gold doesn't matter, it doesn't add or deduct the cash back value, it's equal across the board, and there are no added perks to these redemptions or rooms you booked on the reward.

I'm not here trying to discredit the benefits they provide, but if you want to talk about value or perks for being a loyal hotels.com member compared to the big chain that gives free breakfast/complimentary room upgrades - it's non-existent, as it's just a booking site. But the biggest selling point of hotels.com is their network/footprint as they offer great access and sometimes really good deals at remote locations that big chain hotels that have not penetrated yet.