It still got me puzzled... One of the targets of CRM 4.0 should be the Enterprise segment. I wrote postings about the architectural challenges and from architectural point of view CRM 4.0 should or could work.
Nevertheless, I have not experienced a flawless working addon in Enterprise architecture yet :-( It seems that most addons are not designed to work with NLB setups, clusters, CRM server that are installed on several application & platform servers etc.
Another thing probably forgotten that it doesn't stop with the addon itself. There is no standard environment at your customer. So, another big issues is support! In my opinion a lot of time is wasted to request and find the right person for gettin support.
It would make our work a lot more pleasant if next to an addon that works in complex Enterprise setup it also has good support.
Please feel free to share your good or bad experience in the comments, don't be shy :-)