I think it is safe enough. Since plesk 8.2. Plesk used system packages. You can upgrade it safely. But before I recommend to see the following KB (http://kb.swsoft.com/en/234) here you find list of package which necessary to skip. =) Please create backup before.
Hi suprsidr,
It's safe and recommended that you install software updates.but first you have to check the updates, are you comfort with software updates? If it's not affect the previous saved projects then you have to go with updates.