We have separate beta updates and stable updates. The stable updates are generally very reliable. You get new features sooner with the betas, but they can be problematic (for example the last beta accidentally broke the Platform behavior, but it will be fixed before the next stable release).
Some people struggle with memory usage on mobile devices with Construct 2, but usually from lack of awareness to how images are stored in memory. Your game might be a 5mb download since all the images are compressed as PNG or JPEG, but they are extracted to uncompressed (basically BMP) in memory for rendering, which can easily make it 5-10x bigger in memory than the download size. Because lots of people ran in to this we recently added a memory usage tracker in the Construct 2 status bar. It's just an estimate, but will give you a useful approximate figure (e.g. 5mb download size, 40mb memory use).