For me, The Witcher had two main problems. One was all the pointless back and forth. It's just tedious.
The other problem was the shallow combat. With the stances and the different signs CDProjekt could have designed a really interesting combat system, but instead they went for the simplest, most boring system ever which was made worse by the almost complete lack of challenge. This is somewhat mitigated in the first few hours of the game, if you play on hard, but it still ends up becoming a rote process of mopping up enemies around you.
What it did very well was the art design, the plot and a lot of the writing, and that was enough for me to ignore the flaws. Thankfully the game's problems were more of the boring than of the broken variety, allowing me to have an easier time ignoring them.
In any case, if they manage to improve the combat sufficiently, the sequel could become one of the best games ever. I'm eagerly hoping for that.