My service was upgraded a few months back. It was a nice bump in speed and my bill did not go up, surprising. It was at about 35mpbs and now hovers around 110mpbs (though supposed to be around 200mpbs). I am not complaining.

This would be the second upgrade I've gotten from Time Warner, without a price increase. I started at 50 down/5 up (which usually clocked at 70-85 down, 5-6 up), and they upgraded me to 100 down/5 up (usually clocks at 130 down, 5-6 up). The 20 up is what I'm most looking forward to.

Why are up speeds so abysmal? Is it a problem with infrastructure, or is it throttling because they think most uses for upload is illegal?

Good question, and I don't know the real answer; Ars says that cable providers can offer speeds up to a gigabit per second: http://arstechnica.com/information-technology/2013/12/why-co... but IIRC doesn't specify whether the upload caps are a technical or business issue.

ISPs sell uplink to businesses. They don't want folks operating a business out of their bedroom and not paying for it.

Cable networks reserve most of the spectrum for downstream, based on old usage patterns where people didn't upload much.