Ok, I've got 5 of these printers running moderately hard in a small print farm for the past 2 months. And overall I am happy with them. I like the size, I like how fast they are. I've had a few issues that I needed to contact customer service about and they were very helpful and responsive, even considering the obvious language barrier (you'll see what I mean if you contact them). And the user interface has some features that I appreciate and are not found on printers I've used from another brand.
I've learned a few things about these printers that are certainly not deal breakers, but that a prospective buyer might appreciate knowing.
#1: Upgrade the firmware. When you go to the firmware section of the twotrees site, there is a disclaimer not to upgrade firmware unless your printer doesn't work. Don't listen, just do it. They new firmware is better than what the printers ship with.
#2: 3Dtouch or BLtouch support/integration sucks. If you put the G29 code into your g-code, the printer just does weird things. Once it printed my purge strip at a 45 degree angle. It seems to change my z-probe offset value by 0.2mm, and some other weird things. I just use the BLtouch to set my first layer squish, and level it manually.
#3: Sometimes the printers won't start the print jobs. You'll select everything appropriately, and the printing screen will come up, but it will NEVER preheat or start the job. Only by turning the printer off, taking the SD card out, turning the printer back on, attempting to print without the SD card in, then attempting to print with the SD card in will it work. If that sounds confusing, its because it is.
#4: 2 of the 5 printers I received had Z axis rods that were too long and had to be cut down. You can't do it with a regular reciprocating saw, the metal is too hard. I had to use a grinder with a cut off wheel.
#5: Loose hardware all over the place. When you first assemble the printer, take the time to check every nut and bolt that came preassembled. You will find many that are barely tight or downright loose. Of particular check the set screws on the gears inside the extruder. I had horrible stringing problems on one printer that I just couldn't figure out until I saw a post online about loose extruder gears.
#6: stripped bolt holes. The top frame is aluminum, which is a soft metal. While I was going through and tightening all the pre-installed hardware, I found that many of the bolt holes holding the linear rails to the top frame were already stripped out. It seems that they didn't drill and tap the holes deep enough into the aluminum for the steel bolts to have a good hold, and thus they get stripped out. So, I wound up drilling the holes all the way through the top frame, putting longer bolts in and putting a nut on top to make darn well sure they wouldn't strip out again.
#7: Cheap fans. This one isn't really isolated to just the SP3 or even twotrees. I'd say every budget printer out there cheaped out where they could, and fans were one of those areas. The fans WILL die/become very noisy within weeks of first assembly. The fans inside the case died especially fast. Buy extra fans, get the ball bearing kind, they last longer.
#8: Squeaky z-rod. Get some lithium grease to put on the Z screw rod. Otherwise you'll go insane.
#9: The rigid/corrugated wire management stuff they included is horrible to work with. Toss it. Get a bunch of zip ties (the ones included suck) and if you can some expandable braided cable sleeve. SOO much easier to work with.
#10: Assembly instructions are not great. If you've never assembled a printer before, this might give you a headache.
#11: No instructions on how tight to make the X & Y belts, or really even how to attach them at all. Too loose and you have sloppy prints, too tight and you'll get vertical lines on your prints.
I'm nit picking now. Like I said, overall I like the printers, but they have some definite issues that need to be addressed in order for them to be functional. I'm definitely not a printer snob, I need cheap, fast, reliable machines for my online shop. Two Trees provided the cheap and fast, now it is up to me to make them reliable.