This is an beta release, that's true. Nevertheless, it should be quite stable, but not sure. I had to publish this new release because Adobe published officially its Flash Player Version 10 which was incompatible with swfUpload 2.1.0.
If you upgrade, don't forget to replace all files in the subdirectory "swfupload" with the corresponding files which can be downloaded at http://code.google.com/p/swfupload/ (SWFUpload-Core v2.2.0.Beta1.zip).
If you're not sure if the files have been replaced successfully, have a look at status report.
You should know that ImageField support will come with 3.x release version!
Changes (compared to release 1.1-rc1)
+ feature, # bug, - removed
+ #325845: Flash 10 support(grandcat) Support for Flash 10 added. Note that you have to download again all files from the project page of swfUpload, this is very important otherwise it doesn't work. If you are not sure whether the right files were downloaded & replaced, have a look at status report.