Just so you know, I do not work with the adapter on a daily basis. Not even weekly. My current client has a project that is actively using the SFDC adapter. I am peripherally involved with that project and I’ve helped them resolve a few issues - mostly dealing with performance. By no stretch of the imagination should I be considered an expert on anything having to do with SFDC or the DS adapter. I’ve set up my own SFDC sandbox, loaded data to it, extracted data from it, etc, etc. For what I was doing (simple stuff) the performance was pretty good.
I asked the client the question about the upsert functionality and they said it’s the new feature in 4.? (yet to be released).
With regard to bypassing the adapter I have to say that there is a powerful argument for doing so. The performance of the APEX Data Loader far surpasses what the DS SFDC adapter can achieve. If you’re dealing with a few hundred rows at a time then bypassing the adapter is probably not worth your time. The client is dealing with 25 million “contacts” so performance is important. See this thread as an example.
I’m not convinced that it is necessary to completely abandon the adapter. But it sure does seem slow.
eganjp 
(BOB member since 2007-09-12)