What you can learn about these fora or anywhere else are simple things that validate some opinions or POV. For example, in terms of posts, you will find that some lenses have a lot of positive feedback by more than 2-3 dozen people. That alone shows you one indicator if the lens is good. Couple that with the same zeal through time, and you don't have to 2nd guess that lens. An example of that is the 70-200 f2.8L IS (mk-1). Another is the 17-40L, or 85 f1.8 usm (and 100 f2 usm). Another is the 35 1.4L Sure, you will see some detractors, but in essence, the ratio of those who don't like them vs those who do is small. That's a sure clue to you where that lens really stands. Even the 50 f1.8 mk-2, in spite of its poor construction is up there when it comes to optical performance. All opinions and even test confirm this.
Go to Fred Miranda site, and read the user lens review. You'll see a trend there and that is very accurate too. I bet you're going to find out that it basically matches the opinions here.
The other indicator is when a store stocks it. Or how often it goes out of stock. You'll see how popular some lenses can be. It's also not a popularity contest. Because at these prices, if the lenses are no good, even if they are cheap, they don't move off the shelves.
Looking at the 28 f1.8 usm, you should now have a clear picture of how it really stacks up. One can praise the lens, but without a doubt, the that lens is not as good as a sigma 30 f1.4 or a 35L or 24L. Very hard to argue about those. And there are sites w/c already reviewed and compared them with picture comparisons to boot! So, I can assure you, that the opinions rendered here, can be cross-matched with some pictures of the same subjects and that is a better way to know about a lens.
But if you want to be safe, since you seem to like wides and primes, go for the 24L. It will cost you more, but you will be happy with that. There's nothing worse than having bought a not so cheap (the 28 f1.8 usm is not cheap) and for a lens not to be stellar considering it is a prime. Remember, the 50 f1.8 is cheap but it is stellar. So is the 85 f1.8. Even the 35 f2.0, with all it's fault is very good. The 28mm is neither here nor there. So, if it were me, and I like a prime for my wides, I'd go for the 24L. Until they update that 28 f1.8 usm, it's one of those lenses that very few people like to own. And that is for a good reason. If it were so good, then the opinion would not be so divided. Unfortunately, that alone shows the true status of this lens. For me, that is not as clear as mud. That is as clear as it goes on sparkling spring water on a sunny day.
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'Always in the process of changing, growing, and transforming.'
