I really need to revisit that set at some point. I had a few acquired over the years and currently have the original black/silver style working well after months of repairs. Yet haven't yet taken the time to explore its library of titles but Parsec with the voice synthesizer is really amazing. My first TI99/4A was from Goodwill but only had Space Invaders and I didn't get into it very much.
I have the FinalGROM SD cartridge for mine now, which makes it really easy to transfer games including homebrew. There's also a WiFi/Ethernet accessory for it.