I agree, I personally prefer sites with their own SSL certs, but have seen many that use a shared location. One word of future warning though, with version 4.0 release the shared checkout location will be specificed in the cart to more detail, and the shared location will be based on a number, so instead of something like:
https://secure100.monstercommerce.com/www_mysite_com/for checkout, it will be:
http://secure100.monstercommerce.com/104678/While I am sure some people do not like this idea, here are our reasons:
1) At a root level, the reason for this is part of our imporved internal automation and similar systems. A lot of things that were done manually will be automated, this includes shared checkout setup.
2) This will actually solve a serious problem customers with many domain aliases have had.
In the past, if not using a redirect (which according to our SEO people may affect page ranking), then people hitting aliases or differnet options ato access a url had this problem:
Example - adamstore.com, which also has an alias of pimptasticstore.com
Initial setup would be a shared checkout for www_adamstore_com, so when someone went to
http://www.adamstore.com and checked out, they would go to
https://secure12.monstercommerce.com/www_adamstore_com.
BUT if they went to
http://adamstore.com checkout would take them to
https://secure12.monstercommerce.com/adamstore_comwhich would be broken
Same with the ip address, the aliases (pimptasticstore.com and www.pimptasticstore.com), etc, etc....this was actually a bit of a flaw in the way 2.x-3.x determined shared checkout locations, etc, etc.
With 4.0 this will not be a problem at all, regardless of how the person gets to you store, the checkout for shared SSL will take you to the location as specified in the site settings, which will be using the new format as I mentioned.
Hope that info helps.