While I haven't used one myself I've heard nothing but good things about them. I myself am leaning between a Mueller and a Nikon. From what I've heard they're great scopes for very little money.
I think there are much better choices than Mueller. I have a Mueller Eradicator (a step up from the Tactical) on a 22 and that's a good use for it. It's not a bad scope, but I'm not sure how long it would hold up to the 308 and I'm just not that impressed to be honest. On the other hand Rich at Mueller is a stand up guy. I think that the (discontinued?) Simmons 6.5-20x50 Whitetail Classics that Midway is blowing out for $110-130 are much better scopes. I think you'll find lots of other choices. The Bushnell Elite 3200 Tactical (I have the 4200 Tactical) would be a great choice.
Thud, if you're still shopping, I have the Mueller Eraticator, and it is an excellent scope for the money. The APV is also great, but I wouldn't put it on a CF gun. Mueller may well be the best value in optics right now.
I've got an Eraticator on my .204 Ruger MKII. For the money, it's the best scope I've ever had. Is it a $1000 Luepold? No, it's not but it's not $1000 either.
I replaced a Tasco 8-40X50 that was so poor optically it was useless above 30X. The Mueller is much clearer and on par with an 8-32X50 Bushnell that my uncle shoots with.
Mueller replaced my first Eradicator and I'm pretty pleased with the replacement. My only quibble is the size of the dot, and that's only because I'm using it for a rimfire target scope. The scope was designed as a varmint scope and the mid-size dot is fine for its intended use. Just be prepared for a fairly restrictive eye location at very high magnification.
Yeah, the Eraticator is quite picky on eyeplacement. More so than the Tasco or Bushnell. Pay attention and it's not a problem, especially for bench or (typically) prone varmint shooting.
You should give Mueller a call, I've seen plenty of posts saying that they're more than willing to talk it over with you and they're apparently pretty good about resolving any problems after the purchase (although I have no experience with this as I have fired about 10 rounds with my Mueller)