I've used Kobu's Character Advancement System and really liked the way it handled things. The basic method of how it works is that skills level up in the same way they used to (although the rates at which various skills level up have been adjusted for balance); however, stats increase automatically based on skill gains (each skill can contribute to multiple stats in different amounts, and when you've raised skills sufficiently the stats will then automatically increase). Levels are also gained automatically in the background. Basically it allows you to just play the game without having to worry about getting enough non-major skill increases between levels to get the x4 or x5 stat bonuses. It's also highly customizable, with lots of options regarding precisely how the stat increases are calculated. I used it in conjunction with Oscuro's Oblivion Overhaul (which creates a much more static world) and found it to be very well balanced (for me it resulted in my character being a bit weaker at the start, but then coming into his own at a very gradual and natural pace, and growing to where he could handle even the toughest challenges of the world while still not feeling overpowered). I encountered no bugs or other issues in over 100 hours of use, but it does include recovery options in case things somehow get messed up (basically it allows you to recalculate all your stats based off your current skill levels at any time).