I jumped in. A friend of a friend is a developer for iOS, and he had a couple extra device spots for a beta tester, so I signed up. I upgraded my iPhone 4 and iPad (original) to the iOS5 beta. It took me all of half a second to decide to do it.
The Dangers:
Now, a few days in, I can tell you I will never be so fast to jump in again. At least with my iPad. I just need to know the apps on there work. I lost several apps that are key to my work flow. I don’t have to have most of them on my iPhone, but I use them on the iPad daily. I don’t blame the app developers (And I for sure don’t go post negative reviews on the app store about it!), they should not have to support a beta software. That’s why it’s a beta. I should have updated one and not the other. But I wanted to play with iMessage and sync docs back and forth through iCloud.
But my iPad isn’t a toy. I use it for work. Suddenly key apps did not work. I know that they will work again, but for now I’m out of luck. I am waiting eagerly for the next version of the beta, hoping it magically fixes these important-to-me apps. Take it from me, rushing headlong into beta testing is not smart.
Now running it on my iPhone, that is another story.
The Cool Factor:
There is something narciisiticlly nice about being the center of attention. People gather around as you demonstrate the features they have been hearing about in the newest version of iOS. They cannot get this new thing for months, but they want it and you have it. There are enough parts of the new beta working that you can show it off, but just be sure not to expect glitch free bragging. Invariably, something will drop. That’s OK, this is a beta. It’s not supposed to be perfect. And it is cool.
Useful:
One of the reasons I wanted to do this is to use the features mentioned in the keynote. iOS5 is going to be amazing. I would go on about how cool it is, but I don’t want to say too much.
The NDA:
The Non Disclosure Agreement is pretty intense. I don’t blame Apple. Beta software isn’t perfect, and no company wants people complaining about what may or may not be working. So, I won’t be talking much about it, even though some blogs feel free to say plenty.
In the meantime I eagerly await the next version of the beta, in hopes that my summer won’t be completely jacked up by my impetuousness. I’d roll my iPad back, if I could. But, in the meantime I wait, and use alternative apps to get my work done. Oh, and enjoy a great new iOS from Apple.
Scott Link Media 
You’re very brave. I can’t afford to have a device crippled even for short while – even if I am very very very curious to try iOS5. 🙂 I am very much looking forward to the official release.
So far I’ve found the IOS5 beta on the iphone4 to be pretty stable. I’ve only found 3 apps that don’t work out of 55 on my device. Push mail seems to be sporadic. It will work for a while, giving me a tone when email comes in and putting it in the notification center. But then it will stop working. Turning the device off and then back on fixes it every time, but only for a while. A few emails later and it will stop working again. You can still get email, you just have to go into the app for it. Not sure what the problem with that is but overall I am very surprised that a first beta runs so well.