I have a very-secondhand Kity 439, which is a much more 'budget' version of Steve's 639. It's built like a tank (by modern standards), and it works, but...
Kity 439 micro review
... Like many other budget units, it's hard to keep the infeed and outfeed tables in parallel planes (almost coplanar), and the amount of offset (roughly equivalent to the depth of cut) is tricky to adjust well.
The planer ("jointer") fence is pretty pants - wobbly and very hard to get exactly square. I keep looking at it and muttering as after about ten years of ownership I still can't think of a practical mod to improve it. Once square it tends to stay put, but I do need it to tilt also, and returning it to square again is a pain.
Also frustrating is the amount of snipe from the thicknesser. I discussed this here a couple of years back, and I now think it's mostly down to sawdust blocking up the vertical travel of the infeed and outfeed rollers. Both have a pair of heavy coil springs, like a miniature car suspension, and the spaces above the springs and below the 'axles' get clogged up with compacted sawdust. Because they can't move freely, they squeeze the stock too much, leading to snipe.
OK That was the bad stuff. Mine is umpteenth-hand, but it works pretty well even though the paint is actually cracking off. The motor is still strong and willing, and everything turns as it should. The bearings for the cutter head are massive, and show no signs of play (and they are sealed, too).
On softwood, it does its job surprisingly well. Ditto on American White Oak and Beech, and relatively soft 'hardwoods' such as Idigbo and Sapele.. considering it's probably early 1980s manufacture, and was probably only intended to last for ten years or so, it's ridiculously long lasting. And it has non-ferrous tables, so it sits in a damp garage/workshop with only the cutter block well covered up, and I need not worry about huge rust problems.
Would I get an ancient secondhand Kity 439 again? Almost certainly. Mine was 200 UKP, and needed a complete overhaul, but I learned a lot dismantling, cleaning and fettling it, and it continues to please me with what it will actually do.
General things to consider:
Particularly for thicknessers--"planers" in the land of mangled English--it might be well worth looking for one that will accept a helical block (AND for which such a block is currently being made & available). I don't know enough about them, but I'd hope the actual cutters now have some sort of standardization, allowing third party manufacturers, similar to the system for lathe and milling machine carbide tooling in metalworking.
The reasons for helical heads are well discussed elsewhere, but the single biggest one for me would be getting minimal tearout when processing hardwoods. The simple fact you can put carbide inserts into them would be worth it - I was trying to clean up Teak not so long ago, and new sets of HSS knives weren't lasting for a single thin pass on a 3" piece of stock. I've got knife change down pat now, but it still takes around 15-20 minutes to do them carefully. And yes, I do resharpen them, so I keep several sets handy if I'm doing anything other than softwood. But Teak, and other hardwoods with significant mineral inclusions, too-quickly defeat my present HSS planer knives*.
There's video out there in YouTubeLand "proving" that a helical cutter needs more power than a traditional one (eg. as fitted to a very common DeWalt lunchbox). Despite what these folks demonstrate, I am extremely skeptical that this is the whole story. Intuitively, it doesn't make sense - there's usually only one or two cutters engaged at the same time, and they should be taking a shearing cut, too. I can't do my own experiments as I don't have a helical block for my machine. Even if the extra power consumption thing is true, I'd still get a helical block if I could.
So many different construction choices, tolerances, and adjustments interact in these machines that it's foolish to assume one single cause for any specific problem in use. This must be the same for all of the budget ones. If you buy cheap and new, you might get away with it, or you might be stuck with a machine you simply can't fettle (as too many corners were cut in design and manufacture).
Watch out particularly for parts that ought to be metal but which are plastic mouldings, and bracketry, etc that's thin pressed steel instead of bar stock of heavier pressings. Also the very frame of the machine itself must be dead square and true - again, thicker steel probably equals better.
So, old DeWalt, and Electra Bekum, and possibly Kity all look worth consideration. If you buy new nowadays, all bets are off...
*I haven't yet tried grinding to a different cutter angle, as honing becomes tricky, but that mighe be worth some experiments.
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