I just bought an HL-2270DW to replace a 2140 at drum end-of-life. This review is excellent (here is my short one), Wirecutter recommended it as best cheap laser printer and Brother drivers seem better behaved than most. User manuals are here.
I've have preferred the lower print costs of a higher grade printer, but the Brother model I considered draws too much current for many overloaded home circuit breakers.
Like most Brother printers (all printers?) it will stop printing when toner is "low" -- typically a few hundred pages short of an empty cartridge. With the 2140 I could cover an optical sensor and order a new ($$) cartridge. That doesn't work on the 2270; this page provided 3 options:
- The unscrew and rotate method
- A fiddling with buttons option 
- Use the web GUI to change the Replace Toner printer setting to "continue" instead of "stop"
I like the last one. I used Bonjour Browser to find my printer's IP address, but I don't recommend this . Instead read the Network guide/manual. In OS X I used Open Print Queue I clicked a button called "Show Printer Webpage ...". That did the trick; OS X resolves the Rendezvous URL to the correct network address.
Click printer settings (un/pw is user/access) then change the Replace Toner settings. There are other settings and reports of interest as well .
I left the settings on Stop -- when the printer stops I know to order a new cartridge; I can change the settings then.
PS. The printer is supposed to come with an optional sticker that explains various flashing lights. I found mine floating about the floor. Watch for this when unpacking.
 - Open the front cover and leave open while completing the following steps. - Turn the printer off. - Hold the 'go' button (or "start' button) while turning the printer on. All panel lights should be on. - Release the 'go' button (or "start' button). - Press the 'go' button (or "start' button) 2 times. - Pause. All panel lights should be on. - Press the 'go' button (or "start' button) 5 times. The toner light should be off. (error may be flashing) The paper light should be on or flashing. - Close cover. The ready light should be the only light on.
- Drum Unit is rated for 12,000 pages, memory size is 32MB.
- The Administrator pw is admin/access. You can use this to change both the Admin (admin/access) and User (user/access) credentials if you wish.
- You can give the printer a static IPv6 address (good luck)
- It has NetBIOS support (brings back nightmares)
- BRAdmin uses the printers SNMP services
- It has an FTP and TFTP server with mDNS and LLMNR (who needs all this in a home printer?!)
- It has an SMTP service and a POP3 Server?!! - presumably for notifications (but why POP3?). You just know that this would feature in some evil network hack.
(IPv4) (IPv6) 1 10/100BASE-TX IEEE802.11b/g (Infrastructure Mode / Ad-hoc Mode) ARP, RARP, BOOTP, DHCP, APIPA (Auto IP), WINS / NetBIOS name resolution, DNS Resolver, mDNS, LLMNR responder, LPR / LPD, Custom Raw Port / Port 9100, IPP, FTP Server, SNMPv1 / v2c, HTTP Server, TFTP Client and Server, SMTP Client, ICMP, LLTD responder, Web Services (Print) NDP, RA, DNS Resolver, mDNS, LLMNR responder, LPR / LPD, Custom Raw Port / Port 9100, IPP, FTP server, SNMPv1 / v2c, HTTP Server, TFTP Client and Server, SMTP Client, ICMPv6, LLTD responder, Web Services (Print) APOP, POP before SMTP, SMTP-AUTH WEP 64/128 bit, WPA-PSK (TKIP/AES), WPA2-PSK (AES), APOP, POP before SMTP, SMTP-AUTH Wi-Fi Certification Mark License, Wi-Fi Protected Setup (WPS) Identifier Mark License, AOSS Logo
I wonder if it's running Linux.
 After I ran Bonjour Browser ML persisted in showing the Rendezvous identifier for the printer as a "SHARED" item in the Finder left bar. I had to run BB again, and twiddle with reload services, to make it go away. I think BB might need an update -- in one config screen it refers to "Jaguar".
Update 2/21/2013: I had to do this when the "starter" toner ran out and the real cartridge didn't arrive. First times I tried setting the web config to 'continuous' instead of 'stop' it failed with a 'printer busy' message. I paused the queue and restarted the printer and I was able to change the setting.
Update 4/4/2013: I bought a TN-450 2,600 page extended cartridge, and after 200 pages I have a toner light. I wonder if it was a counterfeit -- though I did buy it through Amazon direct. Alternatively it or the printer may be defective. Alas, it's 4 days past the return period so I'm stuck.
Looking at the 1 star reviews I'm not the only user to run into this.
In the process of reviewing comments I learned of the official way to bypass the toner light from the extensive user manual:
- Press Go button 3 times within 3 seconds to print a settings summary
- You can do factory resets using Go button (see manual)
- I read that pressing the Go button 7 times will bypass the toner warning, but that is not in the manual.
Update 5/21/2013: These aren't counterfeit cartridges, we really are only getting 600 or so pages per $55 cartridge. See: Gordon's Tech: Is Brother running a scam with its HL-2270DW printer and TN-450 toner cartridge?