I've seen several versions of P & P, including the original movie, but I thought that casting in the BBC mini-series was practically flawless.
For example, I don't think I need mention the excellence of Colin Firth as Mr.Darcy.
I thought Alison Steadman was just perfect as Mrs. Bennet, as was Benjamin Whitrow as Mr. Bennet, they were both very funny and skilled.
David Bamber managed to pull off an excellent Mr.Collins, even though he is described as being much younger in the book.
Crispin Bonham Carter captured the essence of Bingley perfectly and Susannah Harker worked perfectly with him as Jane.
Anna Chancellor was, without doubt, the best Caroline Bingley I have seen, so arrogant and opinionated!
And Barbara Leigh Hunt could not have played Lady Catherine more superbly, in my opinion.
Of course, these are just MY opinions, I'd be really interested to hear what you have to say and if you think any other actors could have portrayed the mini series roles better and, naturally, include any others you feel deserve a mention!