One downside to detachable mags is that you often give up one round of capacity to the fixed mags. E.g. in the CZ 550 American line of bolties the fixed mag version of their non-magnums holds 5 rounds, while the detachable mag holds 4. You'll probably find most other manufacturers do the same thing, with the exception of "tactical" rifles (they often will have 10+round mags available), but those usually aren't as well suited to hunting anyway. Most hunting rifles will have mags that are flush to the underside of the stock.
As someone already mentioned, reloading with stripper clips is pretty fast. But if you have a modern glassed hunting gun, you'll find those clips don't work very well. The scope kinda gets in the way.
If you're planning on using this rifle as a hunting weapon, I really don't think the advantages of a detachable mag make much difference. I mean, if you can't hit the deer with the first 5 shots what makes you think the faster reload will help?
If this is to be a paper puncher, the speed of reloading is also probably immaterial. You're not going to get very good groups from firing very rapidly, so short of some time limit in a competition, slowing down to reload might even be a benifit.
As to your specific questions:
1. They are not "bad". Whether or not they are "good" depends on what you want from the rifle.
2. Lots. CZ, Tika, Remmy, Probably Winnie, and probably most others.
3. I think fixed mag has more advantages for your typical hunter, and group-shooter. Detachable mags have their place though.
My advise is this: First decide what you want the rifle to be best at (plains hunting, woods/brush hunting, varminting, long range target shooting, plinking, homeland defense against MZNBs *, ect). This will tell you how important a detachable mag will be. Then find the rifle you like best for that purpose, and then see if it can be had with a detachable mag. If not, either buy it and learn to love the fixed mag, or continue your search for a rifle that you really like that does have a detachable mag.
* Mutant Zombie Ninja Bears