Vika's improvements have been minimal but with women's tennis so weak outside of Serena those minimal improvements have made Vika go from your average top 10 player to the player outside of Serena to beat.
Vika moves better now than she did before and is stronger, it isn't much different to before but she gets a racket on more balls on the run for sure.
She has also added a average but useful slice backhand. It doesn't win her points outright and change up a match like say Henin's could, but it just means 2 or 3 points a match these days she keeps herself in rallies she would other wise have lost.
She plays drop shots as a 'kill' shot more than a lot of top players. Vika this year hit a heck of a lot more drop shot winners. Having not huge fire power some of those short balls this year she has simply bunted over the net for easy points.
The serve will forever be average for me, but there seems to be so few aggressive returners outside of Serena and Maria these days that Vika starts a rally on an even kilt than behind in the point like she should do. Domi was a great example of putting Vika on the backfoot straight from the return this year and not letting the crosscourt Vika groove set in.
What irks me is Vika will most likely get herself 3 or 4 slams throughout her career and could have had 3 this year had Serena not been around. When I think about Vika compare to other 3 or 4 slam winners it makes me . Nothing Vika does now is better than capriati at her street fighter best or Kim at her athletic peak, heck apart from movement she has absolutely nothing on Davenport, yet this is the company I feel she will be keeping career wise when all is said and done.