Have they fixed this game yet?

[bolox]

is this game still very demanding and unfinished?

Yes the sim is still 'demanding' (although what you mean by demanding may be different to what I understand the term) and it is still 'unfinished' as in there are things that could be done better. Official development has ceased but there is a group of enthusiasts trying to fix/improve things (see Team Fusion mod).

AI has improved some since initial release- it is still not perfect (care to name a sim that AI is 'perfect'? -with the possible exception of BoB2).
Also mission builders have now got the hang of how to set AI skill levels for more realistic behaviour, in particular Heinkill's Redux campaigns.