They are lenses, that's all. They are not better than newer lenses, they are just different.
Like many older manual focus lenses they are built to a higher standard of quality, much like the cameras they were attached to. This of course does not mean they produce better photographs than newer lenses, just that they will feel better while you are taking pictures. As mentioned, they focus manually. Unfortunately not many Pentax digital cameras are easy to focus manually. The viewfinders are very bright but that doesn't help with focusing. The older ground glass focus screens were less bright but it was fairly easy to see the lens come into focus. You will probably want to buy and install a new focus screen with focus aids like the Katzeye brand.
Even though the lens coatings were very good in their day, they do not really compete well with today's coatings. You will see higher chromatic aberrations as well as lower contrast than what even the lowly Pentax DA 18-55 kit lens is capable of. They also tend to be a bit more subject to flare than newer Pentax lenses are so you should always have a hood on the lens and be extra careful if you are shooting into the sun. Additionally these lenses were designed for film so they may not work as well on digital sensors.
Even the newest of the Takumar lenses are getting quite old by now and a lot of them have had a very rough life. Things that often pop up are hazy and scratched lens elements, fungus, damaged filter threads, bent helical tubes, and other assorted ills. Some of these can be fixed, some not so well. At a minimum you should consider having them serviced by a competent technicians.
Another problem that is related to their age, as well as to general properties of anything that is manufactured within a range of tolerances, is the fact that you can own a cosmetically nice looking Super Tak 50/1.4 that performs very poorly while your friend can own the very same lens that performs like it was built by elves to photograph fairies.
To summarize, Super Taks are not the magic bullet that some people seem to think they are. They are very old lenses that were designed to compete with other lenses being built in their same time period, not to compete against modern lenses. The honest truth is that the Pentax kit zoom will almost always kick their butt.
However, if your camera is properly set up to focus these manual focus lenses, then they can provide you with a different rendering in your photographs that you may like. It will be a more vintage, lower contrast, more painterly type of rendering than what you will get from the Pentax kit zoom. You may like, some people do. But don't be surprised if it doesn't turn out perfectly at first, or maybe even at all.
BTW, although it may not sound like it I love these lenses myself and shoot them quite regularly with my Spottie and SV. But I also recognize their faults and limitations and am prepared to work with those. Like I said, no magic bullets, just interesting photography with limitations.