This seems like a great extension but I uninstalled immediately when it didn't validate with many errors. Standards validation has been around a long time now and is expected that when your site is "green" (validates with the w3c.org) and 1 module throws a bunch of errors it's unacceptable. SimplePayPal keeps doing the trick, but my clients would probably love to see/download their transaction data. Did notice someone brought the issue up on his forums a couple of years ago;( If issue is resolved I will take a look again and re-evaluate and change this rating accordingly.
I've gone through much of the code and re-vamped it to generate XHTML 1.0 compliant markup and to be OK for strict PHP 5.3 compatibility. The entire frontend now validates as XHTML 1.0 compliant via w3c.org validation. There is one exception: the flashplayer thermometer is embedded via an OBJECT tag and an EMBED tag. These are not W3C/XHTML standard compliant. Yet, there is no way to embed the dynamic flash thermometer without these tags. Hence, this exception to complete W3C compliance remains.