I've been writing Windows Services for a while and they always seem to work fine for things that need to run every day, few times a week, once a month, etc. but I've been lately thinking about going with Windows Workflow Foundation.

However, I am unsure how would they run on a server without some container application (for instance SharePoint)? I worked with Sharepoint workflows before and I always had huge problems, at first with the bugs in the workflow architecture implementation (the problems with sleep and delay) and later when they eventually started to work, they were difficult to manage and change.

On the other hand Windows Services were always quite easy to implement, easy to create a setup for them and install them and they were always quite resilient (they were often working for months without crashing or something else going wrong).

What do you recommend? Please bear in mind we are working in .NET (version is of no problem, if 4.0 brings something new on this subject, we can use it).