I'm surprised at just how badly they are thought of, I had an Astra for 18 months, it was better than my Punto and pretty cheap to insure. Granted it was a bit of an average car but in the 18 months I had it I couldn't really fault it. I don't think there was a single day where I drove it and didn't take it up to the red line, but the engine started first time every time. I happily did a 400 mile round trip in a day to Silverstone and back which included 2 hours sat in traffic with the air con on, and it returned 45MPG, me and my passengers didn't have any complaints with it. Sure there's no heated leather seats and climate control and all the nice luxuries, but IMO it was acceptable for spending 4 hours in each way.
I'm fully aware there are far better cars around and it's not the most powerful car in the world, but I knew that when I bought it and it was pretty much exactly what I expected. I'm sure if you're used to BMW/Merc quality then it will seem a lot worse by comparison but I couldn't fault it for what it was. In 18 months, all it cost me was a set of rear tyres (got a puncture) and the oil and a filter for the service which I did myself. Maybe I got lucky? I seem to be in the minority here anyway...
If I was looking to buy a similar car I'd probabaly look at something else just because I could afford to insure something with a bigger engine, but if I ended up with another Astra I wouldn't be too fussed either way.