And as RC says, never ever change your base output on seo or writing - what works will always work, just adapt slightly and build more in, as that's all G does too.
timemachined, I'm not exactly sure what you mean, but I don't think I said anything like what I assume you're suggesting I said. It sounds way too formulaic for the way I approach things.
If you're referring to the spam detection patent, I recommend you read that entire discussion and take a look at the patent. Some excellent posts in the last few pages of the discussion... but good posts throughout. The discussion does not sound like what you're suggesting. The core idea in the thread, I think, it that you shouldn't fiddle so much that you raise flags to Google that you're testing the algorithm, and the thread suggests throughout that the considerations are more nuanced than that (and could well depend on the optimization history of the site).
With regard to discussion in this thread, it doesn't sound as if hasek747 has been making a bunch of experimental changes so far, which is good... but, going forward, I'm concerned that either frequent changing of the page title, or switching a lot of words as hasek747 suggested,
might cause Google to test for manipulative intentions. The way Google would test might be to drop the ranking of the desired keyword, rather than raise it, and then to wait a while to see if further SEO changes are made. JS Harris, who just posted, describes some of the kinds of results Google might present to you.
So, I'd take it very slowly and gradually. The kind of situation hasek describes doesn't suggest that a lot of onpage change is what's needed. Right now you want to rank for "best widget" singular, but it appears that the title text, and the prominent text on the page, and the only widget-related inbound link are all plural.
On an analogous site I optimized with a partial match domain that had "widget" singular (for which we were dominant), but we very much needed a ranking for the plural "widgets". I wanted us also to continue to rank for "widget" singular. The change was accomplished by getting a single instance of plural "widgets" up near the top, not in either the title or main heading, and just one plural link of "widgets" (that I know of) pointing to the page. Just one... and it was one of the few times I've ever asked for specific anchor text. The link itself had already been offered.
...and will change "Best Widgets" to "Best Widget" in both the H1 title and meta title. Let's see what happens.
IMO, this sounds too extreme. On the page, perhaps switch one of the more prominent plural "widgets" to singular, but leave the title and heading alone... and hope for a singular link, which is what you need. Also, you might change either the H1 or the title element to singular, but not both. I'd take the cautious approach and make the change in the H1, I think, and leave the title alone.
Also, consider a good internal nav link from somewhere inside the site to the page with "widget" singular in the anchor text.
Additionally, to clarify that when I say "it's really not just about keywords any more", what that means in a case like this is that you want to describe what about this widget makes it the "best", but don't use frequent repetitions of the word "best" to do that.
Particularly since the phrase "best widget" is not what I'd call a natural sounding bit of language, you might want to remove one or two uses of the "best widget" phrase, but keep just one or two repeats of the phrase on the page, and then also "best" and "widget" by themselves... say in the area where you discuss quality factors about this widget that make the term "best" seem appropriate. Maybe add a few sentences... but don't rewrite the page... as it's already ranking. For me, the test is always how the page sounds when read aloud. Then, just let it sit for a long while and see if it changes. Resist reacting to changes Google presents to you.
Don't have two separate pages to target the singular and plural separately. If you have an additional page about the singular, it's got to be completely different. Hope this helps. Let us know what happens.
