[screws in devil horns... ]
Provisional applications aren't worth the time. Once filed, you are pretty much locked into what you have filed. And usually ideas change with research and development and your provisional now won't cover it.
But let's say you are lucky enough to capture all the claims of your idea in your provisional and let's also say that it is doing very well and making you good money. When it's knocked off, would you rather defend a patent that you wrote or one written by a professional patent attorney who does it for a living?
I'm not an attorney either (I doubt you'll find one posting an actual opinion here (aside from "hire me") for obvious reasons ... it would be nice to have one giving up the "facts" (or better yet, someone from the USPTO).
Anyway, I do not agree with DrVag and I'm not the only one as shown by the sheer number of Provisional Patents (PP) filled by Independent and Professional inventors (by regular people, patent agents, and lawyers) ... in fact, the USPTO has now even *created* a way for you to extend the use of the PP for up to two years just because of the real value you can gain by going this route.
The two key points DrVag makes for not using a PP is how claims will change and someone is going to steal your idea ... ah, the whole point for a provisional is to make changes and prove it's a winning idea BEFORE you invest the money into a non-provisional patent ... you can't defend/protect a PP and if your idea has so many changes as to make ALL your claims moot, then just file another PP (if you start with a dog and end up with a cat, then you had better start protecting the cat early on).
Plus, if you just go straight into a non-provisional patent there is nothing to say you won't also have changes and knock-offs ... which leads you straight into the patent money pit; regardless, it is not an easy thing one way or other, and you see many products with multiple (original and subsequent) patents; just saying, you do need to consider all your options and that does include Provisional Patent(s).