The problems that I see with Red 99 are:
- Low population - There isn't a whole lot of grouping going on if you aren't in a guild. You may have to traverse a few contents to get to the zone your group has chosen to level. Keep your eyes open as you travel.
- Lack of ports and binds - If you're just starting out I'd highly suggest you play a caster to at least overcome the lack of gear / bind issue. You will die on Red99 more than you do on Blue99.
- Economy - You have to put more effort into buying gear on Red. There isn't 500 people sitting in one zone all day selling everything you need. Brightside is that the prices are lower (on average) for most items. On the other hand, any camps are wide open so making plat to gear up is much easier on Red.
- OOC conversations - A percentage of the population is salty and only seeks to antagonize their foes in the global OOC. Nightly arguments, insults, and linking of gear that "so-and-so will never have" can be expected. I'd recommend you put OOC in a separate window as, if you're like me, you'll probably be minimizing it to avoid such nonsense.
Even with all these issues, I have a great time on Red. I'm not in a guild and I play casually a few days a week. I've managed to gear up 3 characters pretty decently and enjoy the server so much that my 60 Shaman on Blue (full spellbook minus Canni 4) rarely sees any playtime these days.