This forum has no short supply of opinionated, uninformed, dumb-ass commentators so please do not be surprised or put off by any negativity you may encounter. Instead, sift through the posts in effort to identify informed comments; then, make your own decisions.
I am in the process of finalizing consolidation after lengthening my tibias just shy of 9 cm. I am experiencing no problems--things are going exactly as well as I could hope (knock on wood). In my opinion, I was blessed to encounter some of the best scientists and surgeons available world-wide--these are the folks who pioneered external lengthening and who continue to improve the process on a daily basis.
Internal procedures will no doubt eclipse the number of external procedures because internal procedures offer much. However, two aspects of internal procedures that can never match externals are cost and control over distraction.
With external lengthening, you can adjust distraction parameters to correct or improve bone alignment. With internals, if alignment goes awry, you can only stop distraction.
For me, I paid about $22K including everything--surgeries, prescriptions, apartment, utilities, food, transfers, airfare--everything. I could not come close to that price doing internals. This means I probably paid less than $15K for the surgeries and attendant medical costs.