We stayed at the Hilton Shinjuku this past July for the 2nd time and it's a nice Hilton. I'm a Diamond, but no upgrade (we booked two rooms, needed two beds in one room and wanted to stay together so it likely that our request impacted the upgrade). The Executive lounge is very nice - great food, drinks and views. Very helpful staff and the concierge was very thorough with helpful recommendations.

The hotel restaurants are pretty pricey, but there are quite a few other options nearby as well as near the train station. The concierge had a nice restaurant brochure with a helpful map.

For us, it was closer to ten minutes to walk to/from Shinjuku station. The hotel shuttle is convenient, but we found it just as easy to walk most of the time (we took the shuttle a few times after walking around all day and when we had our luggage). As mentioned, there's an underground path to/from Shinjuku - it took us a little bit to figure it out, but it's super easy once you do. As previously mentioned, there's also a subway stop really close by.

We enjoyed our stay at the Hilton Shinjuku and would stay there again!