The K-01 is just fine and most definitely worth it even now, particularly at the low prices you can buy it for.
I shoot grandkids, dogs, sports through high school level, landscapes, macros and many other types of photos with it. About the only thing I haven't tried to do with it is wildlife photography, but only because it looks a bit silly with a long telephoto attached. I strongly suspect it could do that as well if I played around with it for awhile.
It works quite well with vintage, manual focus lenses and focus peaking is certainly a nice plus if you are working off of a tripod. My old eyes combined with shaky hands make working with focus peaking handheld a real challenge so I don't even try.
My major pet peeve has to do with using only the back view screen for everything. First, strong sunlight from behind washes out the view screen. This can be handled by using a hood over the view screen but that option makes the camera more bulky.
The second problem is holding the camera steady, especially with longer focal lengths. Because you are holding the camera out in front of you it is very hard to stabilize longer lenses. The in camera lens stabilization makes this easier to do but it isn't a total cure all. I do use a tripod or monopod with this camera far more frequently then I do with my K10D or K-5iiS when using lenses longer the 90mm.
With the new firmware and short lenses (the Limited 21 is a great example) it makes an awesome street camera. The autofocus is pretty quick and you really don't need to hold it up to look through the display screen if you practice with it. It becomes a great point and shoot if you work with it for a bit. I don't own one but I think that the 15mm Limited would also be a great lens on this camera.
The image is beautiful. Most Pentax camera output is quite exceptional in my opinion. They seem to get the best out of the sensors they work with. I usually work with DNG RAW but I have had really good luck with the jpeg output as well. Just make sure you adjust your white balance (auto white is not bad but not the best) and set the saturation to Natural. Saturation can always be added later in post but IMHO it is harder to desaturate jpegs.
Like just about any camera out there you have to buy it, learn it, use it and experiment to get the best out of it. You probably won't be as as happy if you just pick it up and start shooting without understanding it. A lot of people have maligned the camera just because it isn't a DSLR instead of just accepting it for what it is and learning to use it properly.
Because of what it is there are certain types of photography it is very good at, and others that it can do but not as easily as a DSLR. With the right lens it is a terrific street camera. It does wonderful landscapes. I love it for portraits off of a tripod. I can use focus peaking that way to get accurate focus right where I want. For the same reasons it is a wonderful macro camera.
The autofocus is pretty quick, but not blazing fast. This is really no different than any other Live View camera out there in its age range. The firmware upgrade did a lot to improve this but it will never equal other Pentax DSLRs.
Live View also uses the battery more so battery life will not be as good as your K-5. Not a big deal, buy extra batteries. Charge them and carry them and you will be happy.
Now for the $10,000 question. Will it work for you? I don't know and only you can really answer this question. If you prefer working with a viewfinder, probably not. If you need blazing fast autofocus, probably not. If you want to use long telephoto lenses, probably not. If you are going to photograph college or professional sports you will probably look silly, especially if you use the yellow one.
Other than those things I think it is a terrific camera for the money if you are willing to learn how to use it. For the great majority of people on this forum, if they were really honest with themselves, it is probably the only camera they really need.
It really is one of the most under-rated, used, digital cameras available on the market today. For that reason it can be bought for pennies on the dollar.