Yeah, having debug mode ON in a final release sure doesn't look good. Can we expect this version to be reliable with real money use?
The core of Electrum is very stable. The bug reported by the OP is a minor GUI issue, that only affects address completions.
Small GUI bugs like this are to be expected in any major release, because there are so many different ways to use a GUI, developers cannot test all of them.
In contrast, there is only a small set of functions in the core of the software. A bug there would be noticed immediately.