63
I am a hosting reseller and web administrator with many clients...some of them pay me to run and maintian their websites for them. When given the choice, I prefer to use XOOPS to do that.
When I log into my help desk app, I get tickets submitted stating that the module is no longer working, and when I call the customer and inquire a bit more, I find out they have changed ISP's or answered a phishing e-mail of some sort that compromised their paypal account. Either way, the e-mail address that they were using at first no longer exists, and when this information is changed at paypal, you need to go restart the IPN logging.
This is done as a security measure at PayPal.
As for which version...both work, but I use 1.9 currently.