My LR 4.1 beta version has quit - how do I get my photos out now ?
I assume you don't have a licence for LR4?
If you don't want to use LR any more, download and install the LR4.1 trial version. Assuming you've not used the trial (as opposed to the LR4.1 beta) then that should work for 30 days, during which time export all your images into tif of jpeg.
If you have Photoshop CS5 or CS6, then you can edit the LR files with LR edits in Adobe Camera Raw (without having to export them first) provided you've saved the edit metadata from the LR catalog to the file metadata (e.g. .xmp file if it's raw). Select all the files in LR, right-click and choose Metadata and then "save metadata to file". If you've selected the LR option in Edit Menu, Catalog settings, Metadata tab and checked "Automatically write changes into XMP" then this happens automatically.
Once you've used up your LR4 trial period then you're really stuffed! The only way then of opening the files and seeing the LR4 edits (unless you have Photoshop CS5 or CS6) is to buy a licence.
PS - to add to Victoria's answer - the settings in the catalog include all the edits you've made in LR, but the image files are still there, unaltered. The images data in photo files are never altered by LR.
I used LR4.0, then LR4.1 Beta 1, then beta 2, then the real LR4.1. I'm pretty sure in each case (Windows) the installer just replaced the previous version and read the catalog without problem.
Except that is in the case of LR4.0 - if you previously have LR3.x installed, it leaves that alone, but offers to make a copy of the LR3 catalog, converting it to LR4 format.