GBP195 * 1.2 * 1.6 USD/GBP * 7 = USD 2600+

That's in the grey area for me. A little under a penny per point all told...generally in the range that people look for in terms of a hotel award. I personally tend to do a little better on the middle-category awards.

Other considerations could include the need for the EQN or the points you'd earn on the paid stay, your cashflow vs. pointsflow, possession of giftcards or other discounts, where you are in terms of tracking towards a Travel Package, and whether you might need the points more on another trip where a Marriott property is more of a necessity than it is in London.

I only throw this last one in because I know London fairly well personally and therefore feel comfortable looking around in less-touristy neighborhoods and at local B&B/boutique type places. Contrast that to Asian or Middle Eastern cities that I don't know well and am more willing to pay a "Marriott premium".

All of that said, this is a very good hotel.