Interesting report! I'll plug my own THSR report from last year here, with a few pictures as well:
Tall Taiwan Tales: Fast Trains, Ugly Towns and Turkey Rice
Overall, I'd say THSR is the nicest of the high-speed rail systems I've taken so far, although I gather some of the newest Shinkansen in Japan give it a pretty good run for the money. Re: the taxi/bus parking problem you mentioned, I suspect this is limited to Taichung -- the stations at Taoyuan, Chiayi and Taipei seem to have this worked out just fine. Aren't they building/planning an MRT line from the station to Taichung?