Not a total loss, you get a premium account automatically.
Q. Who has a premium account?
If you've ever spent money on TF2, you have a premium account. This includes purchasing the game before it was Free-to-Play, activating a retail version of the game, or making a purchase in the Mann Co. in-game store.
Q. How is a free account different than a premium account?
Premium accounts have a few extra features, including access to rare and cosmetic items through random item drops, the ability to store more items in your backpack, and more powerful trading and crafting abilities. Otherwise, the gameplay experience will be identical for both accounts.
Q. Who has a premium account? If you've ever spent money on TF2, you have a premium account. This includes purchasing the game before it was Free-to-Play, activating a retail version of the game, or making a purchase in the Mann Co. in-game store.
Q. How is a free account different than a premium account? Premium accounts have a few extra features, including access to rare and cosmetic items through random item drops, the ability to store more items in your backpack, and more powerful trading and crafting abilities. Otherwise, the gameplay experience will be identical for both accounts.
From:http://www.teamfortress.com/freetoplay/faq.php