Sergey,

>You're missing my point. I'm well aware about benefits of using UDF's but I also aware about possible negative effects of using them. The article covers only positive part of UDF usage which may be missleading for the people who aren't aware about negative side.

No, I didn't miss the point. I said, "As always, you need to test what you do for performance." Perhaps Dan can write a part two that goes into more details about performance of UDF's. Or maybe you would like to take that task on? Do you have specific examples of performance problems you have encountered when using UDF's? Perhaps we can all learn from any details you can provide.