Admittedly, I've shied away from CSS masks for compatibility reasons. If you know your core audience is going to be able to see them, then go for it.
There's also the idea of adaptive design: offering an experience for all that offers a similar UX/UI.
To that point, I offer this:
Make the outside of the mask match your background-image or color. Then only have transparency where you truly need it. This approach will allow for a slider in IE7 ... just sayin.
Offer the simplest solution as the default. Then use javascript feature detection to load the SVG, if you've got a compatible browser viewing the site.