I personally disagree that it's a "suitable replacement". Its interface isn't as good, addon preview images don't work well, nor can you even upload soundpack addons. Which I have been waiting for since last october and still no progress.
If I'm not mistaken Sound Packs are not a high priority, prefs and other things are much more important right now so a sound section will come eventually since its not a high priority, and the fact BLG has pref support makes it a suitable replacement.
Also that , the interface isn't good? I have yet to have any issues with it, if your talking about aesthetics, I'm personally glad it doesn't look anything like RTB, or the ancient ugly 3D torque ui that is everywhere, its a clean minimal flat design that is modern and definitely the future for Blockland, the only way it could get better is if it didn't have those rounded buttons that make it look bad.
I have never had preview images not load so thats probably an issue on your side, because previews work fine on the computer I'm using right now and the other older computer I have that I used to use for BL, havent tested it on my old laptop but I assume there should not be any issues there either, if your having issues with it you should probably do a console log and a post about it on the dev thread so they can fix it.