This is starting to really look a lot less like a review, and more like advertising for the author's favorite.
Your example given is simply adjusting exposure or brightness and sharpening. I see no reason to believe paint.net does that any better than LR or anything else on the list, takes a few seconds.
It also doesn't qualify for much of a review when your starting data is wrong, and relying on a post from 2008 about some features.
Selective editing is available in LR, as pointed out, but still isn't updated - things like this make me think 'spam ad' vs 'real review with any substance.'
SafeCast - as you said, it seems to be the same as used by Windows XP. You are jumping to seriously wrong conclusions about "if Adobe decides to make it pay per use" and those are just scare tactics (people repeating them in random forums doesn't make them likely nor true). For a given version of LR already released, that simply doesn't happen. EULAs in general are a bad joke of questionable legal use, but you can bet there would be class action lawsuits if ANY software company decided for an already released version to "just convert it to pay per use." Adobe isn't stupid. While they may make a pay per use version of some software at some point in the future, no software company is going to suddenly make an already paid for product version installed on a users computer into a pay per play, as it would violate consumer rights all over the world, not to mention the amazingly bad publicity such a thing would create for any company. I say this after working in the software and hardware industry for 20 years now. It doesn't make your 'review' any more credible IMO, either. Suggest removing it, or simply providing a link. Your link to info on safecast also - is invalid, which might make someone believe this was typed up some time ago simply as advertising.
So, LR frequently also goes on sale and can be picked up for $100-$150 USD often enough.
Best I can tell, Paint.net doesn't work natively on RAW files, and needs a plug-in to do so, which seems to convert RAW files into something else? Other than that, it's got an active forum which is great, but will only ever run on Windows - no thanks.
Corel products - I'm always surprised to see them still kicking. They've always made some pretty decent software, I used to use Corel Draw and another for a business some years back, and at a much lower cost compared to PS, Illustrator, etc. Looks like PSP is Windows only, but pricing at $40-$60.
Use whatever makes you happy. If the only thing you need to do is what the OP posted, adjusting levels, almost anything will do that for you, Picassa included. And why not include PDCU4 in the listing?
Personally, especially after seeing just how much I've been able to recover some RAW files into something usable, my requirements would be for something that handles RAW files natively, does non-destructive edits on those RAW files including virtual copies, allows for side by side comparisons of before/after editing. WB adjustment, selective edits, good mechanism for organizing, rating, and locating pictures, the ability to apply specific edits (sensor dust healing, re-sizing for export, color/wb corrections) across multiple pictures at once, sharpening and noise removal tools, and Tone curve adjustments. Add in good heal/clone/retouch, which is my biggest LR gripe at the moment for some cases. I have no idea looking at this 'review' which of these apply to most of the above.
Also, what is your perceived benefit of scripting? This is usually done to do batch processing, while LR and others allow batch processing easily enough from the UI, so it may be somewhat misleading.
'Reviews' can be tough work. I'm just not seeing this as an impartial or clear, detailed one at this point - it doesn't give much real reasoning as to your conclusions, besides you not liking Adobe. A single example showing level adjustment - well, why not pick an image and let someone with each of the above pieces of software do their best on it, and see which comes out the best?
Any of them can do what you showed above.
This is possibly coming off as 'anti paint.net' and that's not the intent. Options, especially free ones, are great. But misleading reviews are like the person that spends $1000 on something they've never purchased before - they usually post it's the greatest thing since sliced bread, but give no qualifications for those statements, and this is sort of the same - ratings without much in the way of qualifying them. But at least Paint.net is free, so it's not costing someone $$ to follow along with the OPs advice. Most of the others mentioned (possibly all) have free trials; I'd suggest trying all of them and seeing what works best for you.