IMO, the Conrad's location is extremely good because it is in Chaoyang, and also close to Line 6.
Beijing taxis will certainly not break your bank, but you should avail of Line 6, when convenient. For example, you can do my "one day in Beijing" self guided tour, and use Line 6 to get back to the Conrad (take a taxi to Tiananmen).
The Conrad is also close to Line 10. I'm hard pressed to think of how you would benefit from Line 10 (apart from 国贸), but it is on offer.
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