Engineering problems may exist, but that alone will not deter adoption. Napster had numerous engineering problems. Early intranets (and many current ones) were difficult to build and maintain, but businesses were building them. What about email? Email isn't secure, and is ravaged by spam and email worms. Do businesses use it? We'll see popular adoption of IM in business when business finds a good use for it, not when we have a slick marvel of engineering.