Gifu hashima

Gifu-hashima - what is to see in this stop? I am planning to stay at toyoko inn. Hopefully it is better than Maibara? It was pretty quiet there.
Is the Costco ther worth going to for fun? Easy access?

I want to use this as my pit stop for 3 nights to go to day trips to Nara, Gero, ...
Any suggestions if this is a good stop for hotel? It is on the Shinkansen line.

Poor choice. Less there than Maibara and only one train per hour.

Kindly suggest which toyoko inn would be convenient for day trips to Nara, Gero

Gifu-hashima - what is to see in this stop?

Pretty much nothing. It's just a stop along the line and without a car to take you anywhere else, there's nothing of interest for a foreign visitor here.

Is the Costco worth going to?

I cannot comment on that other than to ask why anyone visiting Japan would consider a trip to an American discount supermarket as a worthwhile use of their time.

I suggest Nagoya is a much better option for you as a base for visiting Nara and Gero. There's are several Toyoko Inns in Nagoya; one being just 3 mins walk from the shinkansen exit

http://www.toyoko-inn.com/eng/hlist_with_address.html#city_nagoya

Gifu-Hashima has some things to see but they are mainly of interest to those who live nearby or those who live in Japan. The sites within the city are very minor.

Gifu-Hashima does have buses to Obocho Inari Shrine which is actually a neat shrine. It's in Kaizu. The shrine itself is small, but it's quite well-known and there are shops lining the entry to the shrine that make it feel festive all year round. It's known for kushikatsu. It's located in a very rural place that appears to be in the middle of nowhere, yet it always draws crowds. This is what I'd recommend to anyone who found themselves in Hashima City.

But Hashima is a strange Shinkansen stop, because it is really only a sensible stop for Hashima citizens. The connections to Gifu City are in fact slower than those from Nagoya, so even for travel as close as Gifu City, Gifu-Hashima is not a great option.