The GR Hotel Esaka is a typical case of getting what you paid for -- I paid under €30 per night for a single ensuite room, and so did not expect luxurious sprawling suites. What I got was a very small (small-even-for-Japan), but clean room. If you're used to travelling in Japan and are looking for a budget hotel that is not a capsule, this hotel is a good choice.
Some reviews have stated that the rooms are dirty, but my experience does not bear this out. The furniture is simply a little old, and the worn edges and slight scratches can give the hotel a slightly shabby look at first glance, but in my room everything was impeccably clean.
The advertised public bath is a nice bonus, though it should be pointed out that the advertised picture represents the men's onsen; the ladies' side is significantly less grand-looking. (But still perfectly fine for a quick relaxing dip.)
Staff was courteous and competent. If you are keen on partying in the city center, the early last train times and the location might not make this the hotel for you, as the distance is too far for an affordable taxi ride. But as long as you don't mind being home while the trains are running, even the location is perfectly acceptable (ten minutes to Umeda, twenty minutes to Namba) and even rather convenient for Shin-Osaka station (1500 yen by taxi).