I test rode over a dozen bikes over the course of several weeks last summer in an effort to get back on a road bike after a 7 year absence. The bike I settled on was by far the most comfortable but it came with Tiagra components - a K2 T9. I decided to go with it because nothing else I rode came even close to this bike comfort wise. I had a budget sufficient for a much "better" bike but comfort ruled - and I don't regret my choice from that perspective. I figured I could upgrade components later if necessary.
I've now logged around 500 miles on it and for the most part they've been fine. I've just started riding longer distances in preparation for ragbrai this summer and they are starting to slip. Yesterday, on a short 25m ride it was bad. I adjusted the rear deraileur and today on a 60 mile it was better but I still got a little slipping. I've read a lot about Tiagra components and overall they are not rated well and several reviewers report serious issues with them as the miles rack up. I'm thinking it may be wise to go ahead and upgrade before doing ragbrai (480-ish miles in 7 days).
I have toyed with just buying a "better" bike but I really love the fit and feel of this bike so that doesn't seem necessary. I was thinking of upgrading to 105's.
I have no clue on how much I should expect to spend or what questions I should be asking.
Any help/suggestions are much appreciated!