Again, if you're pretty minimal with your phone, you probably won't experience significant lag. If, however, you run a ton of MobileSubstrate based apps and don't already use Categories, you will notice a significant memory usage, and this has been confirmed by quite a few of the iNav users in that modmyi forum, whom also backed up their claims with tests using MemTool, SysInfoPlus, and SBSettings memory watcher. There is an undeniable amount of memory being hogged by using iNav but again, you won't notice it if you don't have a ton of MobileSubstrate apps installed and if you had previously been using Categories already, as Categories has a known memory leak (which the creator, BigBoss, has stated he has not gone around to fixing yet).
