Improvements to SD3 since the first release?

as far as I know:

messed with the way that the z axis screw mounts to the motor

aluminum sled for the bed

new board (which is worse/better?? but mostly cheaper)

new heater pad for bed (instead of resistor bolted on)

better software supplied by default

uh..  not sure of what else.  to be honest I wish they would adopt the M3 z axis screw for no banding as a stock thing.  And also make the bed out of a bathroom tile instead of the warp happy aluminum that they use now.

I have yet to find a mirror the correct size, but I've been looking. Also the tile was 48 cents.

And I usually don't clean the bed every time.  I've found that if I ... is the right word season? it, stuff sticks better. After it builds up a thin layer of melted plastic and hairspray, I don't even need hairspray anymore.  Parts stick enough to lift the whole printer off of the ground with no spray, just a hot bed.

When I can run my finger along the bed and feel ridges, that's when I take the tile off and clean it.

Do you need kapton on the mirror?  Or can it go bare?

Glass and mirror are the same. mirror just lets you get a cool view of your extruder in action. lol

I love the way glass bed discussion creeps into every second thread. Seriously, I would only use glass (and do) that is designed for use in high temp situations, like that designed for halogen lights.

EdIt - and as for improvements, from what I've read it seems the heater bed in my new SD3 is a lot more responsive than they used to be. It heats up really quickly, and the newer Z-Stop screw didn't need replacing when I added my glass sheet.

Sketchup is what I use as well.  With enough plugins you can do /anything/.  Just make sure you get solid checker. It makes sure all of your shapes are closed and the STL won't bug out.   I have yet to use netfabb because of it.

Just make sure you get either glass or a tile or mirror to use as a bed, and some binder clips.  I was unable to print a single thing on the stock bed until I did that.  Also get hairspray.  And prepare for a few weeks of adjustment and fine tuning.

Oh, and also plan on making an enclosure.  I have only failed one in twenty prints since I got it (as opposed to working 1 and failing 19 without)

I made mine with some plexiglass at home depot, aluminum duct tape, and magnets/double sided tape.

I have no experience with anything except the red filament that the printer came with and the white filament I got off of ebay.

EDIT: And one other piece of advice.  Get a fan or a heat sink to stick onto the X axis motor. (the only motor not bolted to the case/extruder, it's on the left in the air).  It gets stupidly hot.  I just ziptied a 40mm fan to it and wired it into the same spot that the LED strip was plugged into.

Helifrek, I am a fellow noob of less than two months lineage. Sketchup is free but so is other stuff. There are different types of design programs of which Sketchup is categorized as a "non-solid" modeler. After you design your model you have to ensure that it is solid, i.e. that it would literally hold water. Any leaks or gaps and the printing software will hurl. You must add a few plug-in programs to Sketchup to check and hopefully repair any errors you made. And it is easy to make errors. Trivial things matter, like whether a surface is facing outward (white) or not (blue) trun out to matter.

Even after the Sketchup plugins give your model a pass it may still be rife with errors. So you need to run it through NetFabb or other 3rd party software to further groom it to the point that Reptier (the printing software) and Slic3r (or other slicing software) can interpret it into a solid object. Slicing software does just that, it looks at your model a thin slice at a time and determines the "g-code" or x-y-z position numbers it must run to make that slice. One slice gets laid atop another.

Another approach is to use a "solid modeler" in which case the model starts out solid and is always that way. Gomisan mentioned Rhino. I am looking at Creo Skectch and Creo Elements Design Express both of which are free. Creo Sketch is butt-simple, almost like Microsoft Paint and Design Express looks to be quite slick and master-able with features not found in SketchUp.

I don't have extreme requirements, I  mostly make small electrical parts. I'm a former Visual Basic programmer and SQL database developer so I'm not afraid of learning something new but I'm also 62 and not as sharp as I once was, so simplicity and ease of use are serious requirements for me. A man's gotta know his limitations, as Clint would say.

Anyway, the obvious point is, you might be well served to check out some of the other design software before you settle in on something. Ascertain what kinds of things you want to make, what kind of design features you imagine you might want whether or not you know what that feature might be called, and how much complexity you can tolerate. Some of these programs can do architectural, industrial, electrical, animation (like Pixar) and landscape so they are dripping with features and menus and clutter that no one person could probably ever use.

Ask Ian, Adrian, Lawsy and some of the other gray beards here for their recommendations once you have a basic suspicion as to what type of work you want to do, they can offer suggestions to packages you can evaluate. Watch the demos but remember its never quite as easy as it looks in the demo, that guy is an expert. Plan on an extended and sometimes steep learning curve although you can start knocking out useful stuff literally within a few hours.

Remember to have fun. This can (and will be) frustrating at times but you can also have a hell of a good time and take serious pride in your projects and the expertise you start to develop. This is a great forum, BTW, lots of real good folks here and they are more than happy to lend a hand. Just remember they all have day jobs so it may take a second before they respond and, besides, they're probably helping me with one of my calamities.

Good luck, pal, and welcome aboard.

Take a look on Thingiverse. There are heaps of printable calibration sets and tools, some with metric/imperial measurements, some with nuts and bolts sizes, all sorts of things.