Stating my opinion - I don't agree on reliability. There were so many bugs it was really disappointing and now all the textures and skins have been brought from fallout 3 and reused again. That's why some think it's a dlc. However, there are the voice actings and interesting rp elements that could make up for it. Then again, iron sights and weapon mod kits can all be found in the fallout3nexus.
I agree, but I meant more along the lines of the fact that if Obsidian made a whole new engine, I'd really be suspicious and doubtful of it because who knows what it could have been like. When I heard they were using the same engine, I thought good, because it's unlikely the game will fail, and I've always loved the ES/Fallout 3 game engine.
But yeah I understand how reliable could be a bit misleading. The engine tends to be quite buggy. And the textures are a bit old, but that doesn't really matter to me. Plus it seems lighting has been improved, which will help.