I flew with Cubana from Gatwick to Holguin and then domestically, from Holguin to Havana, and then back to Gatwick again.
I read all the same reviews and, being a nervous flyer, was panicking and honestly didn't expect to get to Cuba alive! But the flight was uneventful. The plane was leased from Europair or something like that. If anything, the pilot was overcautious as at the first sign of any turbulence he had the seatbelt sign on.
If you're flying from Havana airport I'd warn you that (at least when we were there) you had to have your bag shrink wrapped. There is a free facility for this, but the queue was MASSIVE. If we'd noticed the paying shrink wrap bit we would definately have used it.
Compared with Virgin who I think were our only other option for flights, Cubana were so much cheaper it seemed daft to spend our money on the flight instead of the holiday.
I dunno if this is always the case, but I think all the dodgy reviews had put other people off because our plane was almost empty so we had lots of seats to stretch out.
I'd have no hesitations in booking a flight with Cubana again. It's not luxury flying, but there is an inflight film and the food is just as good as any other airline. Also, when the hostesses come round midflight to sell you rum and cigars it gets you right in the mood for Cuba!!