Pretty loaded question. haha, It's a lot of work and it could cost a pretty penny depending on the rails you get. I certinaly wouldn't trust the Hiwin knock off rails on ebay and amazon to do the job.

If you're planning on CNCing your machine and doing any type of "production" or repedative work it might be worth the upgrade. Not having to worry about adjusting gibs it super great and I don't worry about wearing out the commonly used areas of the machine. If you're not planning in CNCing it I honestly wouldn't convert it over. Spend that time and effrot into srcaping the gibs so they fit better. Gibs are a tried and true method that work, but I feel like a lot of these import machines aren't fit together very well and it causes people to get frustrated trying to adjust the gibs.