I don't know if current Tiagra shifters have the thumb lever for shifting to smaller gears, but on the 9-speed versions I never did like them. Felt really cheap. My 2011 Felt commuter has 105 5700 10-sp which feels pretty good for the most part. But I've ridden mechanical Ultegra and DA bikes and the shifters and brakes feel even better on those.
I would love to either upgrade my bike to 11-sp 105 5800, or build a new bike with 5800. Main reason is for climbing. My current cassette is Ultegra 10-sp 11-28 and sometimes I feel like I could use one lower gear on some hills. An 11-speed 11-32 cassette I think is pretty much the same as the 10-sp 11-28 with just the addition of the 32 cog, so that would be perfect for me.
I already have a 11-sp compatible wheelset, all I would need would be the cassette, RD and right-side shifter.