It's less tested than Firmware 4 but there's been no known reports of issues thus far. But perhaps you'll get (un)lucky
Thats good, I would like to give the gift with RTC fully working but didnt want to chance it breaking and not having the cart to give with the GBC. I think I may chance it, I have bought 2 (one for me and one as a gift), both will be the exact same outcome so if one fails, I wont bother with the second and just use F4.
Wish me luck