Gold Compass

• Share prices with other players. A new free Windows app, the Gold Compass uploader, shares your scans and brings back every Gold Compass player's prices and sales for your realm and region. Get it with /gc share (or Settings > Share prices with players), which also shows whether sharing is on. The getting-started guide mentions it, and players who aren't sharing get one tip in chat after their third scan.
• Tells you when there's a newer Gold Compass. Once per login, in chat, if a newer version is out. Gold Compass users in your guild, party or raid quietly tell each other which version they have, and the uploader passes on the newest version from the server, so you hear about updates even if you installed by hand. /gc status shows your version too.
• Up-to-date vendor prices. Gold Compass used to remember what a vendor pays for each item the first time it saw it, so when Blizzard changed vendor prices (wands, for example) it kept using the old ones. It now always uses the game's current price.

Thanks to lostmimic on CurseForge for the first three:

• Vendor prices for materials. Common vendor materials (thread, dyes, vials, flux, coal, spices and more) now count at a vendor's price in crafting costs straight away, instead of resellers' AH prices, even if you've never opened that vendor. Until you do, the price is worked out from what a vendor pays for it (vendors charge 4x that for trade goods); vendors you open give the exact price, as before.
• Make materials yourself when cheaper (new, in Settings, or /gc craftmats): if a material is cheaper to craft than to buy, crafting costs count it that way, a few levels down (materials of materials). Only recipes you know. Buy mats then buys what it's made from and tells you in chat what to craft first. On to start; untick it in Settings to always buy materials.
• The window no longer hides behind unit frames and action bars, and no buttons poke through from behind. It also comes to the front when you click it.
• No more text running into buttons, and no more text cut off with "…". Everything you can read now wraps onto another line when it's long, and whatever holds it grows to fit: Settings labels keep to their column, tick boxes like "Skip 1c margins" are placed by the length of their text, buttons get taller, long item names take a second line in the lists, and the Market/Snipe panel, the Level up banner, the craft panel and the sniper alert all grow with their text. The Buy button in the panel is shorter too ("Buy 129 for 19s 35c"; the item's name is right above it).
• "Show the craft panel" always shows it. With no craft plan it used to do nothing on screen; now the panel opens and says how to start one, with a button to the Level up tab.
• Check the window layout (Settings, or /gc layout): checks every tab with your game's own fonts and lists anything that overlaps or is cut off. /gc diag runs it too, and with debug on each tab is checked the first time you open it.
• Things a vendor sells are never snipes. If anyone can buy an item from a vendor, resellers' prices for it on the AH aren't a real value, so it no longer shows on Snipe or Market or pops up (for example Mote of Magic, thread, dyes, vials, flux and arrows). Vendors you open are learned too, so anything else they sell is skipped from then on.
• Much more accurate sales. When a seller undercuts by cancelling their listing and reposting it cheaper, that used to count as a sale, every time. So nearly everything looked like it sold fast, and "Sells: fast" hid almost nothing. Reposts are now recognised and skipped. Sales start afresh once with this update, and show up again after a few hours of scans.
• A wall of cheap stock is no longer a snipe. When most of what's listed is at the cheap price and there's more of it than sells in about three days (999 slugs at 5c when they usually go for 10c), that's simply the new price, not a bargain, so it isn't listed or popped up. A smaller cheap batch that will sell through still is.
• Snipe has a "Sells" column: the same speed bars as Market, so you can see at a glance how quickly each find resells. Click the heading to sort by it.
• "Sells" filter on Snipe (replaces "Only items that sell"): click to switch between daily+ (seen selling about once a day or more, as before), fast (only items that sell 8+ a day) and any. Right-click goes back. Pop-ups and auto-buy follow it.