GMA is a cheaper option for getting cards graded than the other options listed. While it might not increase the value as much as other more renowned company's such as PSA, it's a more viable option for cards who's prices won't be worth the PSA fees. Current GMA prices are as low as $10/card. PSA's cheapest option is $30/card and the card must be valued at over $500.

As an avid PC big box/small box collector, it would be immensely helpful to download and see all PC & MS-DOS games/prices/release dates in the spreadsheet export so that I can keep better inventory (using pivot tables and whatnot) of my current collection and ensure I'm using standard names for all games in my personal spreadsheets.  

Add some plug n play coleco tellstar stuff and other things from the first generation.

I would love it if you started tracking direct from Nintendo Refurbished models.  They come sealed from Nintendo and can be sold sealed which is a major plus.  

Preorder bonuses are oftentimes included in used game sales to increase the value. Example: Fire Emblem Fates Special Edition with the three character keychains. Some websites such as IGN and Nintendo Everything include pre order bonus guides for yet-to-be released games. Gamepreorders.com seems inconsistent with which games get articles. Perhaps preorder bonuses could be included in the Details section of a game page. Including preorder bonus as a check box for adding games to a collection would be excellent, but I acknowledge a bigger change

Id like to see the current value of the games in my wishlist, so you can more easily determine what the cheapest item in your wishlist is. 

Would love to see the value of my Digimon cards. 

Include the model numbers in download files.