Doddy is correct - I saw that thread too and followed some of the advice there :) Let me update with some extra (and dare I say, important) findings of my own (I own the device since a few months):

1) One can indeed open the tablet portion with little trouble - only a thin sharp object will be required to carefully unclip the back panel (do not go too deep, the thing is stuffed to the brim with ribbon cables and the like) - try not to chip any plastic off, be gentle and patient.

2) SSD is indeed M.2 2280 and can be replaced. Wi-Fi card is M.2 2230. My unit came with a lousy Atheros card which I promptly disposed of and installed Intel Wireless-AC 7265 (look for the model with NGW suffix, that's the 2230 version) instead. Now I've got nicely working WiDi (with Actiontec ScreenBeam Mini 2 Intel-certified dongle), but the Wi-Fi reception, though greatly improved compared to Atheros card, is unfortunately still poor. My old Samsung Galaxy Tab Plus fares much better in the same conditions. I've tried upgrading the antennas (correct connector size is IPEX MHF4 - others won't fit) but there's really no room inside to place extra ones and I don't want to tear stock ones out. I managed to close it with the new antennas inside but the reception was just as bad. I really don't understand why - the casing is plastic and the antennas had great reception when outside of the case.

3) My unit also came with the Acer digital pen. It's powered by a single AAAA battery, has two buttons (one serves for right click and one can be bound to any action via the Acer app - e.g. opening Paint) and the tablet will ignore your palm if you put it on the screen while writing or drawing. It can be a bit tricky though - if you lift the pen too high from the screen, the cursor will jump to the closest edge instead of disappearing, which is a bit annoying. A few months later now the stylus also refuses to work until I take the battery out and put it back in; new battery didn't help. Not sure what causes it, it works great after this "fix"... until I put it away for a few minutes. Not a deal breaker by any means though, I rarely use the thing.

4) The single most annoying thing was finding the correct microUSB 3.0 adapter. I refute the reviewer's claim that an OTG adapter will suffice - unless you use a microUSB 2.0 OTG adapter (that'll work but of course only in USB 2.0 mode). I tried using several USB 3.0 OTG adapters meant for Samsung Galaxy S5 and Note 3 - none of them work. According to a Lenovo tech support thread I've found (it talks about a Lenovo tablet with the same microUSB 3.0 issue, forgot which model), this is due to this port not being actual OTG but rather a normal USB 3.0 repackaged in a micro form-factor. I've found an adapter that DOES work: www.dx.com/p/ly-8005-usb-3-0-female-to-micro-ab-male-adapter-blue-250236 If you must buy from other sites (though I've had nothing but positive experience with DX - shipping takes long but always gets there without issues), look for adapters which people specifically complain about to NOT work with their SGS5/SGN3 - that's how I've found this one. Huge relief, to say the least, I thought my unit is defective or the BIOS needs an update (which Acer has not released so far - now I know why, there's nothing to fix!), and now I can finally use my high-speed USB 3.0 storage devices and USB 3.0 to Gigabit Ethernet adapter. Worst part? This thing costs less than 2 euros, why couldn't Acer just bundle it, it was so much pain to find and acquire... and now I have a bunch of OTG cables to dispose of >_<

I didn't see the usual "maintenance access" description. However, I found in another forum (based in Malaysia), a user managed to access the internals and found the RAM to be soldered but the SSD was upgradable. The user then upgraded to 256GB, DIY style with a faster unit and used the old 128 as a USB disk. The SSD is m.2 2280 size. The same user also said the wifi card can be replaced. The Malaysian version shipped with a digitizer pen, in addition to the case. Users reported that the pen is surprisingly good, although some noted not as good as MS-Surface.