A majority of mods have indeed met with a favorable response throughout the Oblivion community and it's really wonderful to see how gamers use their creativity to perk up the gameplay. However, certain mods, reportedly, tend to cause problems in a game environment that already suffers from recurrent technical issues (in relation to that, we suggest you try the Oblivion Beta Patch). In many cases, installing a particular mod may bring nothing but disappointing results, instead of a satisfying gaming experience. That's why we urge all of our readers to think carefully before adding a specific custom-made update to their version of Oblivion. We also strongly recommend backing up all essential files before updating the game. There's plenty of unofficial junk out there and, in some cases, it would be wiser to avoid the whole thing, as opposed to ruining the entire game on account of a poorly designed mod. From what we've gathered, your best bet is to stick to fully-functional and regularly updated mods.