Howdy. We've been using the Events module regularly for over a year, and we use the PayPal option. We could never get the return from PayPal to work properly.
In other words, the user can click on the payment option and they are sent to a PayPal page, which allows them to successfully enter their credit card information. However, when they try to return to calender page, they get an error. We do receive the payment, though. It's a nuisance, but not a show stopper. I believe that this is a bug in the Events module, itself, and this includes the version that's currently available for download.
I believe that Alan said that he made some fixes to the PayPal portion of the next version of the Events module, which will soon be available for download once it passes the certification process. Whether the return from PayPal issue is specifically fixed, I don't know. Alan can better answer that question. By the way, the next version of the Events module is available as a beta version, and you can download the beta version if you email Alan directly.
I can't speak too intelligently about which level of PayPal works best. Someone else in our team handled the setup and implementation of PayPal. I do know that we started at the bottom rung with PayPal, but this level didn't work out because the lowest level only allows you to take transfer a max of $500 in receipts a month back to your checking account. Please understand that you can still receive an unlimited amount of receipts in the entry-level plan, but PayPal will only allow you to transfer up to $500 out to another account (such as you checking account) per month. By the way, don't quote me on the exact figure for the monthly max. I think that it's $500, but it might be some other close number. Anyway, we had to step up to the next level, which allows us to transfer a lot more money per month, but I don't know the exact amount.
Our organization makes serious use of the Events module on a daily basis, so I'm an experienced user. Having said that, I'm not an expert by any means. If someone else reading this post knows better about the PayPal return issue or about the various levels of PayPal, please chime in. I would be happy to find out that we've set the module up wrong, and that PayPal integration has no issues whatsoever with the current version of the module.
See Ya,
Van