Well, Kobo's can't be classed as a leveling mod as all it does is slow down skill advancement. Progress does this in a much superior method.
True leveling mods would be nGCD (which I can't see past and highly recommend) Oblivion XP and Realistic Leveling. Others that are popular are SPAM and AF Leveling.
Kobus' or KCAS is indeed a leveling mod, but like AF Leveling an outdated one.
Possibly the best realism mods can be found in Kurtee an tejons's threads.
...surely good ones, though I still prefer my own Real Sleep Extended;) Now, tejon makes good mods, but Real Sleep Extended (which is the one Belanos recommends) has much more detail than other sleep mods, like taking into consideration when (morning/day/evening/night) and where (inside/outside, bed/bedroll/other) you sleep - and a lot of other factors. If those don't mean much other mods may suit you better.