I think many people are a bit harsh on Bale. He scores goals, he puts in a regular supply of quality deliveries, and his powerful running with the ball would be a handful for any team.
While Giggs was fantastic and much more unpredictable than Bale, i remember him being more like Nani, capable of moments of sheer genius but often frustrating and inconsistent.
I think Bale is a lot like Valencia, he doesn't have the skill of Nani or Giggs, but then Ronaldo doesn't have the skill of Messi, but it still does not hinder him from being consistently very effective. That is the key in my view, it's not always just about talent, but how often the team really benefits from their contributions.
Personally i think we would be a better team with Bale in it. I am not suggesting we should go for him or anything like that, before anyone starts, i am fully aware of the cost and other potential complications. But hypothetically i really believe Bale on the left and Valencia on the right would be a truly devastating duo, and regularly so. I mean what strikers would not benefit hugely from such a consistently high quality service?
Nani is a special talent, and he is the type of player needed when games are tight and a bit of unpredictable magic is required. But he is often still too inconsistent and unpredictable to know what you are going to get, his crossing is very erratic, and he is overly greedy at times. Valencia and Bale would be much more dependable, and a regularly effective threat can often be enough to significantly improve the performances of a team.