Here's some data points from my recent stay:
We used The Access Narita to go from the hotel to Narita. It costs 1200 Yen (200 for the subway, 1000 for the bus) vs. 3100 for the direct airport limousine bus. The Nishi-Shinjinku is a couple minutes walk from the hotel -- the front desk clerk said it was easier to walk outside than go through the tunnel, and it certainly was easy (2 lefts). The subway ride was ridiculously easy (even with rollerboards), but the signage at the large Tokyo Station where you do the switch is confusing. When you get off the subway, turn left and follow the Yaesu exit signs. You will see Yaesu North, but you don't want that. Keep going a little further to you reach the next corridor and find an escalator on the right. Take that up one flight and you'll see Yaesu South. That's what you need. Just walk outside the building and you'll see Bus Stop 7. There was a small line at the bus stop; we made the first bus, but I would give myself time to wait for the next one just in case. Allow yourself about 40 minutes to get from the hotel to the Access Narita stop. From there, about an hour to the airport. The bus is as comfortable as the Airport Limousine bus (you get one big piece of luggage below, and anything you want to carry-on the bus). The three of us saved US$60 by taking this subway ride, and I'd say it was a no-brainer.
The hotel itself is good, but not fantastic. I picked it because I wanted to use points and I knew my credit-card Diamond status would get me some useful perks (unlike, say, my credit card status at the Hyatt across the street). The lounge is good. If you're staying a few days, you'll probably wind up at breakfast there because the main breakfast room feels too busy and the extra selection is modest (and the lounge has a fresh-squeezed OJ machine). What we did one day was book the free (for Diamonds) Japanese breakfast and then "top off" our breakfast with a visit to the lounge (they knew we were doing both but didn't care). I would not say the Japanese breakfast was delicious, but it wasn't bad (I'm not a huge fan of Japanese breakfast foods), and it certainly was an interesting cultural experience. So peaceful and zen-like compared to the bustle of the main breakfast room. And with the ability to grab more "normal" breakfast food afterwards in the lounge, there's nothing to lose by trying it.
While not advertised, we found a nice selection of mini-sandwiches and desserts at around 1 pm in the executive lounge (I thought "tea" didn't start until 3). In the evening, the 6 to 8 pm happy hour (with booze) has decent food. You could make a meal out of it if you wanted to and weren't so picky. Try the fancy Asahi draft dispenser -- it fills your glass from the bottom! And the beer is much better than canned Asahi.
We found the frequent free shuttle to the Shinjuku Station helpful. It's not a long walk (15 minutes?), but the shuttle is easy. And the area immediately around the hotel is sleepy -- the station is frenetic. Try a "belgian waffle" from the Manneken store next to the station's Hilton bus stop: best cheap dessert in Japan.
Overall, the hotel suffers a bit from being too busy (it's big and the locals seem to come for their restaurant specials), but it's not a bad place to use points or status.