With the new system, you can set up notifications for all types of things including when someone adds you as a friend. Go to the Manage Settings page to set your preferences. Also look for the icon in profile pages and journals to track updates and changes. Just check in to your Message Center to keep up to date on the LJ activity that's most important to you.
Paid and Permanent account holders have the most subscriptions available and also have the extra options to get notified when a user uploads a new userpic and when users add new comments to individual comment threads. We'll also be expanding the types of subscriptions that are available only to Paid users over the coming months. Visit the FAQ to find out the different limits and options for each account level.
Please feel free to spread the word to other Paid account holders you know. The engineers are still working out bugs in this complex system, but if you find something you think we should know about please leave your feedback on this post in lj_releases.