One of the reasons behind SiteMatch is to ensure your deep pages are indexed by Yahoo. But if your pages are search engine friendly and the navigation is not prohibitive to the natural spiders, then SiteMatch is not needed for that purpose.
A thread at HighRankings named Out Of Sitematch & Bump In Y! Ranksings discusses one person's story with SiteMatch. This individual did not renew his SiteMatch subscription and soon after saw his rankings improve. From my understanding of the post, it seems like the site's homepage was not included in the SiteMatch results. So he wasn't ranking for his most important keywords (important is subjective here). I am not so clear as to why, neither is he, his vendors or YahooMike. It seems like he did not submit his homepage URL, and thus the page was not included.
I was under the impression that the natural crawl would pick up other pages (if search engine friendly) even if they were not submitted to SiteMatch. Speculation? I rather not, but you see where I am going with this.