Is slab foundation really that big of a deal?

I'm going to be purchasing my first home within the next couple of years and have been window shopping to get an idea of the market in the area where I'm going to be moving. The problem is, the majority of the homes within my budget are built on slab foundation-- not with a crawlspace. I've been told to NEVER purchase a home on slab foundation because in the event of a problem, it would be much more expensive and difficult to make repairs. Is this true?