I've tried Campag, but only briefly so I'll limit my comments to the fact that it's different to Shimano and I'd only really say one was better than the other after a longer-term test.
But some people here are comparing low-end Shimano with high-end Campag or vice-versa, and you can't really do that I think : I have used different Shimano shifters - and there's considerable difference.
I changed Shimano 8sp Sora shifters to 9sp Ultegra shifters on the Winter bike at the end of last year.
Not because of the Sora thumblever, which I found perfectly reachable from the drops, despite the oft-repeated 'you can't change up on Sora from the drops'.
But because the Sora lever was so damn uncomfortable to hold. Alright with thick Winter gloves, but the web between fingers and thumb became really sore on lnger rides with thinner Summer mitts.
The 9sp Ultegra shifters are a much more comfortable ergonomic shape, and I think 105 9sp is the same shape.
I have 10sp Ultegra on my Summer bike and the shifters are a slightly different shape, which again is pretty comfortable. Again I think 10sp 105 is the same shape.
But the shift quality of 9sp Ultegra is nothing like that of 10sp.
That shifts snick-snick so quickly and easily by contrast.
9sp Ultegra is better than 8sp Sora, but not a huge lot better.
The 10sp is miles better.