I'm surprised, but happy to see so many folks in this thread stating their experience rather than just being scope snobs.
That said, I've had a little bit of experience with these Tasco's in 3-9x40 as well as have a couple of hunting buddies that have used them in both the 40mm version and 50mm version.
The first one I bought was a little over 5 years ago. I had bought a cheap muzzle loader from a friend and had no idea if I would even like muzzle loading. So I wanted to get into it cheap in case I didn't like it. I topped the gun off with this Tasco Bucksight from Walmart that was $30 at the time. Got it zeroed and the gun shot amazingly well. I was really surprised by the groups. Anyway, took it hunting a time or two that year, but never really used it much. I probably shot it maybe 100 times during the off season, but not too much. Before the season the next year I made sure it was zeroed and took it out hunting. I killed a fairly large buck with it and was impressed. It seemed to hold zero well. I used it for the next several years too. It seems to have good glass, very similar to the Leupold VX-I that I was using on another gun at the time, holds zero, and just all out works well. I never did a box test on it, but I have my doubts that it would be repeatable, however, I wasn't using it for that.
The only time I ever had it lose zero was after I had sighted it in and let it sit at the house for months. I took it to the range a few months later, and it was a couple of inches off. Now, that said, I had taken the gun out of the stock to clean it as well. So I'm not sure if that was what made it shoot differently, if it had gotten bumped around, or what the deal was. I feel like it can't have been the scope since that is the only time I've ever had it lose zero, and it wasn't very far off then. I didn't use that gun this year, and haven't shot it in several months, but for the past 4 years the $30 Tasco has held up great, and I've killed a couple of deer with it. Including that first one that was fairly large, and since then a nice 11 pointer that is my largest deer yet. I really have no complaints about this scope. Now I would probably go with a nicer scope if I could afford it such as a Burris FFII, Vortex, etc. because then you get better glass and the peace of mind that it will probably be more reliable, but if I didn't have the cash for one of those, I'd not hesitate to run one of these Tasco scopes again. I also have to say, the glass is plenty good to get you well past legal hunting light.
The second one I had, was when I had my Leupold VX-I go bad for the first time in the middle of hunting season. I sent it in for repair, but I needed a scope for my 30-06 to finish hunting with. I bought one of these, mounted it on my 30-06, and shot it for the next month. It held up well, and did great as expected. Once I got my Leupold back after the season was over, I remounted it back on the gun and ended up selling the Tasco to a friend who still uses it to this day. This one is probably 4 years old.
So I've had good experiences, and while I do believe you can get better scopes in the $150-200 range, I would certainly run a Tasco from Walmart before not having a scope. I also don't find them to be nearly as bad as most of what I've read online.
My friends have mostly had similar experiences and I know several guys using these. One friend has one on his Knight muzzle loader that he hasn't touched the adjustments on in several years. He kills deer year after year tagging out, usually with mostly large bucks. He doesn't worry about the scope at all as he has never had a problem. Several others have had similar experiences.
The only two I know of that may have possibly gone bad, were two hunting buddies bought T/C Omega Z5's from Walmart. Both bought these Tasco scopes in 3-9x50 to mount on them. One shot great right out of the box, and the other one was shooting all over the place and they never could get it sighted in. I wasn't there for the initial sighting in, but saw the targets. He assumed the scope was just trash and took it off. He then mounted a Bushnell scope that was proven to be good on there. I was there for this sight in procedure and the gun didn't shoot much better. It was shooting 4-5" groups and hitting all over the place. He finally got about a 4" group and got it centered somewhat over the bullseye. He decided this was good enough and has killed several deer with it. He still claims that first Tasco was bad, but I have my doubts. I will admit that it didn't shoot even that well with the Tasco, but it shot so poorly with the proven Bushnell, that it leads me to believe it is most likely the gun, not the scope.
The next failure was the other one who had bought the z5. He killed several deer with it the first year. The second year, he killed a deer with it, then missed a deer. Now, I will admit that he is a very good shot and it's rare to here of him missing a deer. He shot at another one and missed it as well. He came to the conclusion that the scope had gone bad and that since it was cheap he wasn't going to even mess with it. He never shot it at paper, he just took it off and put a nicer scope on there. So I don't know if this one really was bad, or if he just missed the deer, or what exactly happened here.
So, I'm not really confident enough to say that either of those two were for sure failures. That coupled with the about 10 good experiences I've seen with this scope leads me to believe they are pretty decent. I mostly run nicer scopes on my guns now, but I do still have that Tasco and I don't believe that cheap budget scopes are nearly as bad as you read online. That said, 98% of the guys I hunt with run scopes under $100, most of them are really hard on their guns, and it is very rare to hear of a failure. Most of them are Simmons, with a few Bushnells thrown in, but they are owned by Bushnell, and I've had similar experiences although maybe slightly better with Simmons.
