All of mine (except for one in 2002) have cleared, and I'd guess that about half of mine were waitlisted. So with well over 100 VIPs, VIPOWs, VIP03s, eVIPs and now SWUs, I'm batting better than .990.

IMO (and others' opinions, also), the more I and D inventory, the better your odds of getting the elusive C inventory. Booking well in advance greatly helps your chances.

Get a subscription to www.expertflyer.com for a mere $99/year or $10/mo and you'll get unlimited queries to look for C and other hidden inventory. This is helpful because you can search for upgrade space before you book a ticket, eliminating the need to ask the agents to check each and every possibility. You can set up an alert and expertflyer will email you when availability opens up (I have no financial interest in EF, just a very satisfied long-term customer).

Good luck.