I don't have one..yet but the Optiplex series are very hot right now for upgrading and mods for gaming. The 3020MT especially is being sold because of it's upgrade path for PSU, GPU, SSD. And when paired with a PSU upgrade and a GPU upgrade makes a very acceptable gaming system and this on a computer approaching 10 years old. And for more proof check YouTube videos for 3020 tutorials and reviews, there are a ton of them.
How long have you kept an your system up & running? If you have kept it running longer than 5 years what do you use it for? To view older questions, please click here.  
"DS: What is the longest you have kept a Optiplex?"