Hi featherhead,
Having done the Sea Safety Survival course, I'd recommend it to anyone going offshore and especially anyone equipped with a liferaft. The last place you want to be learning about one of those is out at sea in a howling gale when your boat is sinking.

What the course taught me most is that almost the last place you want to be is in the liferaft, as Ramona says. No way I would step into one unless the boat is sinking - but you definitely don't want to try climbing into one if you can avoid it either. Still, it's a damn sight better than bobbing about in the water.
In their defence though, remember that a liferaft is built to help you survive against the worst the sea can throw at you, not to be pleasant. While no doubt an inflatable or dinghy can be a Good Thing, you need to think about some of the situations you could potentially face. Will an inflatable protect you against windchill? Will you be able to protect yourself from exposure to sun, rain and spray? Does it have inbuilt features to help prevent capsize? If capsized, will you and all the contents remain in the inflatable or will your entire food and water supply simply float away? If you manage to right it, can you get back in? If your motor won't start (or you're too buggered to row) do you have a sea anchor to help stop you being blown away?
A liferaft won't guarantee survival but at least it has features that'll help in all of the above scenarios. Of course, in the end, it's up to you to weigh up the situation and make the decision you think best in your case. These are just some points for you to consider along the way.