My copy of the 50L is nice. I have actually used the 1.4 and the newest 1.8 as well, so I have a base for judgment. All of the lenses make acceptable pix, and in the end, as far as truly discernible results, what you are really paying for with the L is that half stop. (I also feel that the 1.4 is definitely worth the price over the 1.8.) I thought I was paying for L build quality as well, but as it turns out, I broke my lens fairly easily. I bumped the lens hood straight on with a car door, and the front retaining ring (on which the name of the lens is printed) snapped off. It is plastic, while all the other Ls I have seen are metal. Canon repair was extremely rude and evasive on the phone, and one angry fellow even hung up on me once after giving me attitude. I have never had such outright aggressive and rude behavior from a corporate someone on the other end of a phone. I was finally able to determine that they do not follow the practice of by-the-job sliding pricing. Instead, every item in the catalog has several repair price tiers, into which various types of service are organized. They would not tell me into which tier my repair fell, but they did tell me what the three prices were. The cheapest one was $300. The most expensive was about $650. They absolutely tooth and nail refused to give any real information, and appeared to have very little knowledge of anything camera related, even once I was transferred away from the call center to someone who supposedly knew something. All they did was state over and over that they need the item in hand before they will talk about anything. It felt like they were trying to trick and strongarm me out of my money rather than serve a customer. So, I ordered the part for $35, and had my local guy install it for $30. After this experience, I will not ever take my camera there for anything except free sensor cleaning...and that's only if my friend is headed down there with his cameras as well. I wouldn't actually drive for it. I don't even want to buy anything from Canon.
Other than that horrible plastic front ring, the lens does have typical L build quality, though. The two things that have broken on the L are both plastic parts. I also have a crack in the focusing scale window...but that's OK, since EF focusing scales are 95% useless anyhow. HA! When someone uses the line "It's OK it broke because it was useless anyhow", it's time for a redesign on two fronts.
I did not even know there was an AF problem with this lens. I do shoot wide open very often, but don't shoot *very* close objects that often. However, I can remember some specific shots in which I shot close, wide open, and AFd on one shot with the center point (always), and got a sharp picture. Have never used an EOS film camera, so I have nothing I can post here.
Your name is not Dan, is it?