Pretty reliable. Spark plug breakage and exhaust studs breaking are the only two fairly common issues. One thing to keep in mind- the alternative is a 6.0 Powerstroke. Any moderate repair on one of those will cost more than an entire replacement of a V10. In shopping, I'd be price-sensitive. A big, gas eating V10 isn't everyone's cup of tea, and resale $$$'s should reflect this.
*I've often joked that if we lived in perfect, Dodge would do the pickup styling, Ford would do the interior and chassis design, GM would provide the powertrain... and Toyota would build it.