In the past I've been discouraged from filing provisional applications (in the US), but the new "first to file" provisions of the "America Invents Act" would seem to make a provisional application a wise choice.
Will filing a provisional application secure a filing date for my invention?
The AIA is not really a first-to-file system. It's more of a first-to-disclose system.
That is, after public disclosure, you have a year to file. Publishing in a journal can beat a later-filed provisional application.
A provisional patent application will secure a filing date for your invention, BUT the filing date will only be for the subject matter you disclose in the provisional patent application. If you make a mistake in your provisional patent application that must be fixed later, then the new subject matter added in the non-provisional patent application will NOT be able to claim priority to the provisional patent application filing date.
See http://www.patentwizard.com/ for more information about provisional patent applications.
After March 2013, when the last phase of the AIA will enter into force, there will - for reasons of vesting a date of invention - not be a difference between filing a US provisional application and filing a priority application in any other jurisdiction.
The disadvantage of a US provisional is that it is only a place holder, for which you have to pay more than $100 to achieve just that. If you file in other jurisdictions you have several options: 1) not paying fees, which in many cases will still give you a filing date and filing number of your application and which thus allows you to use the application as a priority application for a later PCT and/or US application. 2) pay a filing fee + a search fee. With this option, which is available in some jurisdictions, you will get within the priority year a novelty search + a (preliminary) opinion on the patentability of your claims. This can thus help to decide whether or not it is worthwhile to continue the patenting process, or whether or not you have to adapt your application. In some countries (where a so called patent registration system is available) you will also automatically get the patent, which you can enforce in a court.
Hence, filing a US provisional may be an option, but you should also explore other options which are available to you and which even cost less, or which provide more information.
