Well for our product (at least right now) you would still need to use another 3rd party module such as Catalook or the Subscriptio tools to handle the actual process. But there are multiple options within the registration module that could be useful. A few come to mind.
1. Use multiple registration pages for multiple subscriptions (possible but might not be needed depending on your requirements).
2. Redirect to different URL's based on their answer. So for example on the registraiton page you might ask 'Sign up for Subscription A, B, o C'. Then specify within the modules Dynamic Events area to redirect them to different pages based on their response. You can also send out different emails based on their response etc... This might be useful if you redirect them to a paypal or subscription payment page based on which subscription they would like.
3. You can have the module show/hide questions based on their user roles, so if they choose 'Subscription A' it would give them their fields for updating their registration that are different then a user who signed up for subscription b'.
4. Role addition/deletion based on question response. Just like #1 with URL redirection there is the option to give them different roles based on their response. The real key though would be enabling that role after payment was made, or this feature might be part of the catalook/subscrtipion tools process as well (ability to add them to a role after payment).
5. Depending on what other module you used for payment you might be able to use Dynamic Registration to gather the correct details. Dynamic Registration has the ability to pass all of the forms values to querystring or session variables, therefore you coudl pass all of the details to the payment module that would then process the payment etc..
Just some ideas, like I said we are working on a cleaner in-house integration with at least Paypal/Authorizenet for subscriptions but its about two to three months out.
If you want a quick demo you can check out www.betasprings.com (login as host/dnnhost) and get a better idea of some of the features. Also, we outline on our demonstration site with Dynamic Forms /Dynamic Registration how you can integrate either of these two modules with Paypal but I don't think it would handle your subscription implementation though.
-Chad