No real draw-backs, but most of the time only extra-features.
Some are incompatible to FMCB (but it is not necessary to have, if you have a chip,... But people love the OSD.).
Some chips also interfere with programms, for example the MI/MI-Clones with USBA, if Macrovision is on.
Bad for those with an old MI-Clone, where this couldn´t be changed.
Another thing is the online-thingy. You need to disable your chip (if it doesn´t do it on its own) if you want to play with an original online, or you need to patch it before burning.
Some other things, but you´re good if your chip can be disabled.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux