If you wish to download all photos from Flickr, the only way to currently do it is using a third party plug-in as Flickr does not offer this option. I tested the approach below and it works well. There are about 10 steps.
1. Go to http://www.java.com/en/download/installed.jsp?detect=jre&try=1 and ensure that you have the latest version of Java installed for your browser. I use Mac, Windows and Sun OS machines and this step threw me off as technically all Macs come with Java installed. However, for the plug-in to work, I had to download another version. Just follow the steps on the java.com page and you should be okay.
2. Log into Flickr and click the Sets button (next to Photostream). You should see something like this. Click on the large "Create your first set now" button.
3. You will get the window below. "Select All" your photos below and drag them into the pane above, then name your set. I called it "my set". Save your set.
4. Open a new tab within your browser and navigate to http://www.flickandshare.com/ ... click the "Start Now" button on their page and follow the prompts to log into your Flickr account.
5. You will see the set you created in Flickr like below. Ignore the big blue buttons, those are ads and keep their site free of charge.
6. After you select your set, the next page is shown below. Click on the "Get your sharing link" button.
7. The next page is shown below. Now click on the "Open It" button on the bottom right.
8. The next page allows you to proceed and download all your photos. Click on the "Download the set" button in the bottom left corner.
9. You may get a few warning messages like the ones below as you are about to run the Java plug-in. Just click "allow" or equivalent to give permission for the program to run. Here I'm using the Mac Safari browser so your messages may be different.
10. Finally, you will get a page that will allow you to "Browse" and "Download" the files.