On a crop sensor camera such as your 7D, the 28/1.8 is a super lens. That lens' weakness is largely that it's a bit soft in the corners, especially at it's largest apertures. Most of that is cropped away using it on a 1.6X camera. It's a very nice, compact, mid-grade lens. Similar to your 85/1.8, except a lot more compact and has a nicer lens hood (bayonet instead of a clip-on).
The 50/1.4 is the third lens in the trilogy - 28, 50 and 85mm - great for crop sensor cameras. Don't worry about the focus breaking too much, other than getting the lens hood and using it, along with some reasonable care.
There are two reasons that seem to be why it's focus fails some of the time:
One is if you override it manually a lot. Simply don't do that. If you want to manually focus it, turn off AF at the switch before doing so. Or just use AF.
The other common cause of failures seem to be hard bumps on the focus ring... If you store it with the lens hood reversed, that protects the focus ring pretty well.
Some folks also seem to think it's a good idea to always set the lens to infinity so that it's barrel is fully retracted. I don't know if that makes a difference, but I'm in the habit of doing that on all my lenses anyway. Can't hurt.
My 50/1.4 was bought used about 7 or 8 years ago, sees a lot of use and is still working just fine. It's always had the hood on it (came with it).
Lensrentals.com published failure reports on the lens a couple years ago. Fully 1 out of 5 or 20% of theirs had to go in for repair in the first year. However, rental lenses are constantly being shipped all around the country and probalby don't get the care you'd give your own lens... Might even be used without hood a lot. So I take their info with a grain of salt. Besides, I'd rather have a lens crap out during the one year warranty period, to get it fixed for free.
The Sigma 30/1.4 certainly seems a good alternative. There are the calibration issues with it, which it might even need to go in to be serviced to correct (might be too much to Micro Adjust). The Sigma is two thirds stop faster than the Canon 28mm. Despite that, I opted for the Canon instead because I also use full frame and film Canon, and the Sigma is a crop only lens. It even vignettes a little on the 1.3X cameras. It also is heavier and larger than the Canon lens, uses a larger filter too. I like that my 28, 50, 85 and some other lenses can share 58mm filters. My other lenses use 72mm and 77mm filters. None share the same size filter as the Sigma. (I also find it odd that the Sigma 50/1.4 needs such a large filter. It's big and heavy, compared to the Canon.)
You will see some subtle differences in your images with either the Canon or Sigma 50/1.4, compared to your 50/1.8. The two f1.4 lenses will give you better saturation and contrast, less flare, and nicer bokeh. It's not a huge difference, the f1.8 is actually pretty good for the money. USM or HSM focus will be faster and quieter, but mainly it's also more reliable and accurate.
Keep in mind that all these lenses tend to work best stopped down a little. The two Siggies are probably the best performers wide open. The 85mm is pretty good too. The 28mm I'd stop down to f2 or 2.2 at least. The same with the Canon 50/1.4. They improve dramatically if you do that.
The 135L is a wonderful lens. I use it for portaits on 5DII and occasionally for sports on 7D. It's a "must have" lens for me, on FF. It's not so critical to me on crop cameras.
Consider the 70-200/2.8 IS "mark I".... It's a fine lens too, that can be had for a whole lot less. The main difference of the Mark II is a bit smoother bokeh, and it take teleconverters much better, especially the 2X III (add another $500 for that, though). It also has 3-4 stop IS, compared to 2-3 stop. I'm still using my "mark I" and have no plans to update anytime soon.
If budget doesn't allow, or you want a more compact lens, the 70-200/4 IS is a superb alternative. Might be plenty fast, particularly if you also have faster primes to compliment it.
Haven't personally used the 17-55/2.8 much (I use a 24-70/2.8 instead), but it has a lot of fans. Seems a great lens.
At best, the zooms are f2.8 lenses.
But if you don't get 17-55, your widest lens will be a 28mm or 30mm "normal". Is that wide enough for you? If not, you are looking at another lens, such as Canon 10-22 or, my favorite and "value pick", Tokina 12-24.
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