There isn't one airline in the world that is perfect or has absolutely ideal conditions for cabin crew, and a lot of members of this website choose to attack the down sides of a particular airline, and in some cases make them a lot worse than they seem. It's an excellent community to vent & to learn a bit about the industry, but everything has to be taken with a pinch of salt.
bmi has it's difficulties, and at the moment is going through a bit of a rough patch in testing out new ideas & product "enhancements" which isn't going down too well with the crews. Now it seems the company is like working for any other no-frills outfit, however you can progress onto more senior positions or longhaul fairly quickly if all is to be believed that mainline has an extremely high turn over of staff. Longhaul is only going to grow at bmi, with the airline regularly looking for new destinations from LHR and lobbying for open-skies between the UK & US. Any longhaul expansion will of course depend on management pulling their finger out and getting us some more planes, but it will happen in the forseeable future.
I can't speak for conditions as I don't work for bmi but bmibaby, but I can tell you it's definately worth giving it a shot. If you don't like it after a year, having a respected carrier like bmi on a resumé will look pretty good if you wanted to go for BA or any other major carrier. I started with what was then called British Midland Commuter, and have always liked the idea of working for a smaller airline, but having instilled into you a sense of pride for your company & providing an old-fashioned style of excellent customer service, I think evident in the high training & uniform standards that we have.
Once our brand has been sorted, I think bmi has incredible potential for expansion, it's just a shame management don't always make the best decisions, but as stated that's the same as at any company.