I/O freeze on databases (SQL VSS)

Our company is considering a new backup product that is an all in one sort of thing (file system, AD, SQL, etc). The product relies on VSS snapshots to create the full backups for the SQL databases. This causes an I/O freeze on the databases that usually just lasts a second or two, but can take up to 60 seconds (per Microsoft, I believe). My question is how bad are I/O freezes for databases? Also, is there any way to determine how long the I/O freeze will be? I would think it would depend on a number of factors including: the size of the database, activity on it at the time, CPU usage, disk I/O, etc. I have only been a DBA for less than a year and have not seen this myself, but my coworkers informed me that we have customers who do bulk data loads and in the past even a 1 second I/O freeze on the database will cause their jobs to fail. We have voiced our concerns to management, but it is likely they will purchase the product. Thanks for your help!