The GH is still walkable, depending on the season (your definition of walkable is probably different in June vs December) - however, it's mostly business or government destinations nearby. Still decent number of restaurants and places to eat, but I'd take the MTR or a taxi to go shopping. Very much depends on what you want to be doing in HK.

The Exhibition Centre MTR station is not far - go out the back exit, through the Exhbition Centre, and it's across the street via elevated walkway giving you easy access to Admiralty and the East Rail Line. Not quite as convenient as having the MTR directly accessible without going outside like the HR TST or the JW, but good enough for me. Then again I tend to visit in the cooler months, so YMMV. Not ideal if you need to take the Island line however, as you'd need to switch trains at Admiralty or just walk to Wanchai station a few blocks away (again via elevated walkways). For me it happens to be an ideal location as it's actually easier to get to my family's flat from the GH than from Admiralty.

As I mentioned above, it's more expensive but the base rooms are also bigger. Your call on whether you want the extra space, or if you're counting on a suite upgrade at other properties. If you're looking at HK island properties and cost is an issue, have you looked at the Centric? Haven't stayed there myself, but the North Point property is consistently cheaper than both the HR TST and the GH since it's not very "central" to anything despite the name.