1. Yes it has an email client and an IRC client.
2. A preview version is kinda like a beta
3. yes fully functional but expect to hit a bug on occasion (I haven't found any yet, but they do of course exist) it is a preview version after all.
4. Yes it can be registered now, but you'll want to download the final version later.
5. I believe its 40 bucks but its the best software I've bought in a long time
IE I swear is the AOL of browsers

Learn the mouse gestures (ctrl B for help) and the keyboard commands are great
Inline search is really nice (in a webpage hit the / button, and in the lower left a text field will pop up so you can quickly search for a string)
You have to play with it for more than a day or two to really learn to take advantage of it
Gilthanaz
Did you delete the old directory after uninstalling?
When you uninstall it may not delete all of the config files, and they may cause a conflict.