Have been about 7 times and love it but each time I see changes and it is becoming more European. You used to be able to walk down every street and hear live music through the windows and often just join them, now it is chart music - I suppose they now want what we have. I have driven right down from Havana to Santa Lucia. Recommend a couple of days in Havana especially Hotel Nacional - lovely gardens and vista and then go further down the coast.
Personally I wouldn't choose Varadero - went there last year but only because it was the nearest main place to Havana and because I was going to be by myself I didn't want to travel too far. Varadero is not Cuba and lacks the character of other places. Apart from a quick visit to Trinidad wouldn't recommend staying there either - too touristy.