What happens when you start Picasa-web-albums?Picasa-web-albums), you are immediately re-directed to Google+ photos.
When this happens, at the top of the screen, for a few seconds, there is a message saying:
"Click here to go back to Picasa Web Albums."
But if you do something in Google+ photos, this top banner message disappears, and the only way to get it back again is to close and re-open Picasa-web. This is tedious - it's a waste of time opening one website just so you can re-direct back to another one.
How to skip the re-direction messageTo use Picasa-web-albums, without being sent to Google+ photos, you just need to start it using this link: https://picasaweb.google.com/lh/myphotos?noredirect=1
I'm going to put it into the sidebar of my blog very soon, so I have easy access to it.
Is there a problem with using Picasa-web instead of Google+ Photos?You might wonder if there is a problem with using the old Picasa-web-albums instead of Google+ Photos.
In short, the answer (for now anyway) is no, there is no problem - and I don't expect there to be one anytime soon.
You still only keep one set of photos in your Google account. It just happens that Google now have two pieces of software that can access these photos. One is Google+ Photos, and the other is Picasa-web-albums. And they both work on the same underlying pictures and photo-albums. So it won't cause you to run out of space, or to have duplicate copies of your photos.
And Google still need to maintain Picasa-web-albums because there are a substantial number of Blogger users who choose to be anonymous: Google+ photos simply will not work for them, because it absolutely depends on having the photos associated with an individual, named persons profile. (And I'm pretty sure that there are no easy ways to transfer ownership of photos from one Google+ profile to another, either, in the event that you want to transfer ownership of your blog.)
Of course we don't know if this will last forever - but my best guess is that you can safely keep using Picasa-web-albums for a good while yet.
Transferring your blog to another Google account's ownership
What is Picasa vs Picasa-web-albums - a basic introduction
Creative-Kit photo editor works from Google+, if not from Picasa-web-albums
Options for showing photos in Blogger