OK, Python ones... Well, I can tell you my experience but it might not be typical (& probably too detailed and picky like many of my posts

assuming I even have time to type anything in before going back to being chief dish washer and van driver...)
I started investigating this product after searching and seeing many positive reviews here on TFF. My only available sink faucets were kind of weird brands and the Python support people told me it wouldn't work as they didn't have an adapter for my make of faucet. I finally decided I didn't think that was correct, so risked a few bucks to buy the brass adaptor and it turned out to fit my faucet just fine. I then got the whole product with the gravel cleaner and a long tube that goes down the hall to the bathroom and a green tee valve that lets it drain or fill your tank.
The two huge, wonderful things here are the long hose idea (because years ago I was just too stupid to ever think of simply having a long siphon tube that could reach a tub, duh!) and the valve that can switch between drain and fill. Well, for me, the first idea (which anyone could do just by buying a long hose) turned out to be the most solid help. Whereas the second idea I use a little, but not most of the time.
Most of the time I just put the gravel cleaner end in the tank, run the other end out to the flower garden and just suck on it to start the siphon. Then I clean some gravel as it drains. One thing I -do- like about the Python product line is that its easy to buy different size and length gravel cleaning tubes and everything fits together nicely.
Then, when its time to refill the tank, I just screw the brass adapter into the sink faucet and start running tap water directly back into the tank, adjusting the temp to a rough match. Note: in my case I'm quite comfortable with the water that comes out of my hot water heater being ok, but some don't like this and therefor don't want to use a mixing tap for their refills - personnally I have no problem with it. I put half my needed amount of Prime dechlor into the tank near the beginning of the refill and the other half at the end (just to copy RDD

) Its nice to be able to just stop the tap at various levels if I want to play with plants or scrub tank walls. I sometimes still use a small bucket for the final topping up after I've put the hose away.
Overall I judge it to be a huge simplifier of the water change process. But then I was pretty stupid and clueless about how I did those operations years ago, lugging lots of heavy buckets.
Now, since I've been doing this, I'm not sure the power of the siphon pull is quite as much as I'd like. I can get a fairly decent churn of the gravel inside the clear gravel cleaner tube and most of the time this is good enough. There are times though when I find myself thinking that a closed water cycle system would be nice - there's a video of one that some guy patented out there on the net - one of these deals where a powerhead creates more sucking churn in the tube-head and then the cloudy water runs back through a poly filter before returning to the tank. I'm sure I could devise one but it would no doubt be cumbersome...
~~waterdrop~~