Well that may be your experience, but mine is a little different.
MCE has never crashed on me. I certainly experienced crashes in the past when using MediaPortal.
Also, MediaPortal completely refuses to start on my sister's PC, unfortunate as she doesn't have MCE and I do think it is a good alternative.
For an HTPC I agree, high quality DVD scaling is great.
However, for simply using the PC as TV to save space on the desk, it is hardly a deal breaker.
MediaPortal has a lot of advanced features that MCE doesn't.
However, for the basic use case described at the start of the thread, I would have to recommend MCE for its ease of use, given that the poster needs to buy a new windows license anyway.