Speaking as a longtime TF2 player (October 2007), I for one enjoy the various updates and the new content it brings. Yes it hasn't always been perfect, but it's kept people interested and playing for far longer than if there weren't any updates. Besides, I like trying out the new gear. Since the unlocks are meant to be sidegrades, they're (mostly) well balanced with the stock items and encourage different ways to play rather than better ways. It's not meant to be a "pay to win" game.
If new potential players had no interest in the game, they wouldn't have downloaded it in the first place. It will more likely be a repeat of when the game first launched: a huge influx initially to see what the fuss is about, then it will taper off as people move on. Sure there will be some idiot hackers and griefers, but they tend to exhibit short attention spans and will soon move on to other games to troll (besides, Valve has stated that they're going to keep a vigilant eye out for such players). However, there will undoubtedly be some players that like the game so much that they'll settle in for the long haul. Instead of shunning them, we veteran players should welcome them in. After all, what is a multiplayer game without a thriving community?
I bought TF2 as part of the Orange Box, which means I only spent $20 or so on the game. It quickly became my favorite multiplayer game (and still is), and it has since provided 1000+ hours of fun for me. If I had to do it all over again and I could choose between buying it or waiting years for it to become free, I would buy it again in a heartbeat.