I use a very Puckett-ized BibblePro. I think I may be at the point where I've spent more on plugins than I did on Bibble. If you haven't looked at them yet, check out
Bibble Plug-in Homepage - Nexi . Some of the free versions are included with the Bibble download.
Using Bibble+plugins it has become very rare for me to have to use an image editor like Photoshop. Plugins I use often are Percy (to correct perspective when shooting lighthouses), Ansel or Siggy for exposure, Sadie for saturation, Sharpie for sharpening. Sometimes I'll use Roy to try and boost the sky without impacting the ocean too much.
The 'no undo' thing is a hassle that they have taken quite a bit of grief about. They have said it's one of their more requested features, so most of us expect it in v5. Another one is the way they save the settings. You have to jump through hoops to have multiple correction versions for a file. And even if you move the file, Bibble will still apply the settings you used on it before. I think you have to rename it, at least, to try different settings.
I'm pretty sure that buying v4.9 now means a free upgrade to v5 when it comes out.