I actually struggled to think of a product that *really* sucked - I mean, I didn't enjoy VB3 much, but it was still an important product that my former employer's business was dependent on. I did however port their code to VB5 at the first opportunity I had.

Then it struck me - Exchange Server 5. That was something I really struggled with. We bought a server from Dell with Microsoft Small Business Server edition on it. That was basically NT4 Server with restricted versions of SQL Server, Exchange and a few other things. Everything else was fine, but Exchange 5 really did crash a lot, the tools for managing it were minimal. And we had less than 10 users - god only knows what it's like when you have hundreds on it. I assume Exchange 2k and later are better (in the same was SQL7 was way better than what came before), but I left the company before that server was upgraded.

Thing I love best is everything .NET really. The smartest thing MS ever did.