been away for 3 years, anything changed?

OMG - stay AWAY from Sintron - PLEASE!!! just seeing that name makes me cringe...

we ordered one of their kossel kits - What a NIGHTMARE!! Printed parts were terrible - as in unusable. Some of the other parts were very questionable as well. In the end, it never got completely built and we ordered a different kit from elsewhere.

In all honesty - do not buy from ebay at all.

If you are interested in a kit printer, take a look at FolgerTech https://folgertech.com/ - based in New Hampshire USA. Decent kits for the money, can easily be upgraded to make them even better (fully open source), and there is a fairly large user base for support. I have built 3 of their kits - the 2020 Prusa i3, the Kossel, and the FT-5 large format.

If you would like a pre-built, ready to run printer, you may be interested in the Print It Industries 8.10 https://www.printitindustries.com/colle … 3d-printer. Well made machine and worth every penny.

As for heatbeds... the Print It Industries Hale heatbed is the BEST!! (for an 8x8 bed size) https://www.printitindustries.com/produ … -8-heatbed I have it on 3 of my 5 printers... the other 2, well, one is a kossel (round), the other is the large format (12x12)

OH yes lots of changes.  IMHO a lot more choices especially in the under $500 price tag.
The i3 variants are still a good choice but there are lot of cheap chinese kits out there pay your money take your chances.
The wanhao and mono price brands are prebuilt and have a good rep they both offer i3 versions.  The way they save money is no connectors so increased reliability  but harder to troubleshoot and change out parts. I have hearn no serious complaints about these.

As heartless said the folger tech brand are kits and decent machines . I have had one of there 2020 I3 for over a year . And just ordered one of there FT5 kits.

Any sub $500 printer will have shortcomings.  But there are often funds available to fix the problems and upgrade.
The biggest change in the last 3 years is availability of material many more materials are reported usable for making parts . Low temp nylon , PETG ,higher temp higher strength PLA, a load of filled filaments and even  printable wax for casting. So these days easier to find one self  collecting filament.
This is an exciting time for 3d printing and design.
Tin

The other change is solidoodle went belly up so the sd 4 that was selling for almost a grand 3 years ago is on the used market.  and a few guys here started printit industries to support the machine.

at the $ 150price point you are buying a pile of parts that you may be able to build a kit from . Expect a part or two missing or not working. documentation will be minimal at best and from mainland china  likely no support. Do not even expect that someone in factory assembled and tested one.
Even at the $250 kit price not a lot of margin for QC/QA customer support etc.
I would not buy a kit direct from china imho too risky  if you expect is to work as purchased.  If you buy a $150 kit from the factory expect to spend at least another $100 to make it work.

Like I said somehow monoprice and Wanhao  are selling working machines for $200- $379

Thanks all.

I've had two Solidoodles. I wouldn't touch one even with a 10 mile pole. Wouldn't want to use one as a base for DIY printer since in my experience the frame of SD3/4/Workbench was too thin and flexed causing backlash but that's my anecdotal evidence and I could be wrong. But I udnerstand how some would find it fun to go that route.
Thanks for the warnings.

Is there a big difference between the MK2 PCB heatbed and MK3 aluminum heatbed performance to consider one over the other?

What about nozzles? Few years ago I had the impression that many praised the E3D too much without giving others a try while others said the "j-heads" are just fine. Have opinions changed here? Personally I only care about ABS and PLA.

And again can't find much info about acrylic vs steel frame difference. FolgerTech sells both acrylic and aluminum extrusion frame ones. Since cost is even a bit less than for acrylic frame, what's the difference really, assembly aside?

Those are some perfect prints, I can't disagree. But in my book it's not really a "SD4" when you replace the entire gantry. I never made a proper investigation on why the frame was flexing but I think it was the carriage being misaligned (the 3d printed parts). A properly printed carriage with bearings instead of bushings which the stock one uses would make the left and right part more parallel which would reduce stress on what the carriage was attached to (the frame) which would reduce or eliminate flexing of the frame.
Anyway, I don't want to get into the whole SD4/Workbench issues discussion, I have PTSD from that.

Can I try increasing the print speeds with an aluminum extrusion frame design? If yes, how much have you guys tried speeding up the print successfully?

PS. I'm interested why anyone would choose the Acrylic Folgertech i3 over the 2020 aluminum, it even costs more.