1. Lag is hit and miss. It's usually not bad, but as it was pointed out, it's been funkier lately. It helps that an awful lot of it's already stored on your hard drive, and that you're instanced; you aren't running around with other random characters in your area, it's just your party, so it keeps the churn a bit lower. There are patches occasionally; ANet pops out fairly frequent updates to various things. Major cities are limited to a certain number of people and then another "district" is created, so that one never gets too full. I've never hit a situation where it was so bad that moving around was seriously uncomfortable in a town (and maybe only once or twice outside of town in my case).
2. Hard to say for sure on the age, but most of the people I meet are in the 20-30 range.
3. One of the things about GW is that a LOT of people play female characters, so I don't think as much of that comes through (it happens, but it's pretty easy to avoid). I had one male warrior dirty dance with my warrior once, and occasionally there's some dirty jokes around. For the most part, though, I haven't hit a lot of this. If you have people making comments at you, you can change districts and just get away from them.
4. I can't help you here from the WoW side, but I thought the controls were pretty easy to catch onto. My husband came from WoW and had a little bit more of a learning curve than I did, but he also started with Factions which gets you going *very* fast.
5. Yep!
6. I think I'd put it at 9/10. As for like/dislike...
Like:
Grahpics, character design, general look of things
Gameplay (every minute of it can be fun, and you still can get enough gold to get what you need)
Clean separation of PvP and PvE, with a few fun things sometimes that overlap the two (and characters can go from PvE to PvP)
If you don't feel like playing with other people, you can take henchmen with you to fill out your party
Dislike:
People's mouths don't move during cutscenes! (it's a stupid thing but drives me nuts)
There's a lot of people who complain in this game - I tune them out.
My 15 year old stepson plays, and it's great - we play together sometimes, and when I'm not around, he finds groups, and doesn't have any problems. Granted, I'm pretty mellow as a "parent" goes, and it helps that I got him hooked on the game to begin with. There's no reason at all not to let him play; the worst someone can do is make a comment at him, and he either ignores it, leaves, or starts mouthing off himself.
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It's a heck of a lot safer than many other online activities, and for the most part you'll just run into other gamers. It also helps that a lot of people assume for the most part that the player is male (I don't know which is the case with you!). I've actually had trouble convincing people I really am female in real life.
No one is going to be able to know where you are unless you tell them, so stalking you down isn't a worry at all. If someone annoys you, put them on your ignore list. It's very easy to avoid annoying people in this game.
Another good thing would be to find a guild full of good people; in my case, I'm in a guild with mostly family and close friends, which is really cool. It gives us a fun group to play with that's totally safe so to speak, and in the case of my stepson, it gives him a group of people who I know are okay to hang with.
Anyway, hope this helps.
-Kel/Eli