I'm thinking of switching from shared hosting to VPS. What I'm wondering is how much support do you get with a VPS? Are you responsible for updating your software, such as PHP, etc. ? Or do you get the same support as you would with a shared hosting plan?
Also, what other benefits are there to VPS vs. shared?
It depends on the provider. They vary from self-managed to semi-managed to fully-managed. But each provider may define these terms a bit different. I personally would consider a fully-managed server to more or less give you the same management or more of a reseller. You just may need to request the update to your control panel or PHP or whatever ... but if the host offers full management and supports that software they usually will update it per your request.
Most won't install 3rd party software without a fee.
I use VPSColo.com and they are a VPS provider directed at people that more or less want a reseller account but with the power of a VPS. I do a lot of my software updates from WHM just because it is so easy.