Latency is lower with a built in modem. IME the lag that a phone wifi network and an extra layer of routing adds is noticeable for certain things like RDP.
>High speed rail is almost always a serious money loser.
Passenger rail is a public good, just like tax-funded public roads (which also don't make a profit, by the way.) Both are necessary for an effective and fully functioning transportation system.
>Since Japan introduced high-speed bullet trains, passenger rail has lost more than half its market share to the automobile.
This is largely due to an increase in rural car ownership since the 60's and the closure of unprofitable rural lines. The profitable Tokaido Shinkansen's ridership continues to increase, with 75% of passenger trips between Osaka and Tokyo using the line. The Shinkansen between Tokyo and Hiroshima, which is a comparable distance to that of LA to SF, carries more than half of the passengers between those two cities.
http://www.jrtr.net/jrtr48/pdf/f06_Tak.pdf
It seems to me that California High Speed Rail will have the greatest impact on medium distance trips where it is too far to conveniently drive and not cost effective to fly. For example, it may become more practical to commute between the central valley cities the Bay Area.