Do you find websites like chesstempo useful for improving tactical skills? I've been using chesstempo for quite a while solving lots of problems per day. What I noticed is that I don't feel that my tactical skills were improving. My results in tournament games were not improving either.

However chesstempo's estimate of my rating is more or less accurate (around 1950). 

So the question is - did such websites help you to improve your tactic skills? if so, how many positions/hours per day were you solving? Did they provide accurate estimation of your rating (comparing to your real-life rating)?
I have not played enough or practiced enough on ChessTempo to really notice a difference in my tactical ability, but I am probably certain that if you spend enough time and I am not sure how long this is (it varies for each person) that your tactical skill will improve over time.  I also never paid attention to my rating on ChessTempo as I do not know what my actual rating is.  

One thing I am certain of is that ChessTempo and other similar websites or puzzles in books will teach you to stop and think before making a move no matter what or will teach you to look for a tactic — whereas before, I would make the first move I saw without thinking.

In the end, it probably does improve your tactical skills, you just have to be patient and not assume that your tactical skills are not improving by the number of games you win or lose.  We often grade ourselves on whether we win or lose and I believe this is a big NO-NO. Especially if we lose, we often assume that we have not improved tactically, strategically, etc.