Not using VSS integration gives you a "Crash Consistent" point in time snap. You will be able to recover everything except any writes pending in memory on the server. But to that point, if you're recovering an entire snap, losing a second of writes is not your biggest concern at the point. VMware and Windows have logs to ensure if you do try to startup a crashed instance, the outstanding IO's will be roll forward/backward to the last known good point in time. Most people don't use VSS snaps because of performance and stability issues on the server during the quiesce process on the server.