Lightroom can completely replace Photoshop for most photographic needs. I will only use Photoshop for a "photo" if I need to do any type of fakery-type manipulation to it. That's more a form of painting, illustration or compositing rather than "editing." Stuff not normally part of a traditional photographic workflow.

Using Lightroom is also completely non-destructive as all edits are stored as metadata.

If you want to continue to use Photoshop and you would not use any editing features in Lightroom, it may be too much for you.

You should definitely keep a separate program for quick viewing, regardless of what you use as a library/asset management app. The two types of programs are distinctly different and in my opinion, diametrically opposed. It is simply not possible to have one program be very good at both things.

In that light, I use Lightroom for all my management and library browsing. For quick image viewing I use a program in Mac OS called "Xee" which is very much like very old versions of ACDSee - it doesn't have a thumbnail browser and it's insanely fast compared to other tools. It also supports pretty much every image format under the sun, including all my old Amiga IFF. However, I don't use this program, Xee, to browse images that are in my photo library folder structure. I just have way too many images and the UI in Lightroom is much better suited for finding things than browsing the file system.

Xee, and even Lightroom for that matter, allow you to quickly open an image into another program.

Based on your first post, I still think Picasa and Lightroom are your two best options, with the possibility of the newer ACDSee Photo Manager or ACDSee Pro as third and fourth options (wow has ACDSee changed a lot in the past few years!). You can then still use a fast Explorer-based viewer if neither of those suits you in that regard. I'm not certain if the new ACDSee versions still tries to do that like the older versions used to.

ACDSee Pro however costs $169 which is only 30 less than Lightroom - that would take it off the table for me. The other version is $70 versus Picasa's free. But, if Picasa's bug is as you describe, that's something horrible to have to live with - unless of course you can avoid using its viewer and pick something else for that part of your usage...