Here's my trip report from 2 weeks ago:
http://www.flyertalk.com/forum/showthread.php?t=414612
If you just consider Sheraton Taipei on its own, it's a great hotel. Rooms are renovated. (The room I got at Westin was better than Sheraton's. Didn't get upgraded to a suite
. On the other hand, Sheraton is often visted by government officials and guests. So I can imagine the suites to be nicer). Spacious lobby and good restaurants. Great front desk service. Easy access to MRT (only few steps away) and that line takes you directly to the city hall without changing cart. If you want the best value (w/internet), I would go with Westin.
Not sure about 101. Never made it to the observation deck.
Enjoy!