This is what our site(revvu) is aiming to do. Much like reddit, users are afforded the opportunity to vote reviews up or down, giving more useful reviews more weight and reviews of less value a smaller amount of weight. Eventually users will build karma and legitimize their opinion throughout the community.
As either Alexis or Aaron of reddit said "it's just a website, it's just a list of links."
In building our startup I haven't come across any monumental, super mathematically/computer science involved problems, but it's still been extremely challenging and fun. I'd say the challenge/fun comes more from trying to do all the things you listed at once, instead of any one of them singularly.
If nothing else, CSS and IE will teach you patience.
This guy is incredible. I worked on some UAV/UGV systems at my uni and heard of quite a few teams using X-Plane as a simulation environment for their UAVs. As stated in the article the simulator actually tries to model what's happening with the aircraft instead of using look-up tables based on full size aircraft, making it much more useful for modeling model... (small scale) aircraft.