Guild Halls

How exactly do you attain a guild hall? What are the uses of having one? Thank You.

You'll need Celestial Sigil to get one, they drop from HoH afaik, or can be bought from the Guild Hall itself (via the Guild Halls NPC in Lion's Arch and Kaineng Center) for a pile of platinums.

Having one didn't really have much other purpose than Guild vs Guild PVP before Factions, now there's options of doing 1-8 vs 1-8 player friendly PVP, and ability to have all the essential trader NPCs in the hall as well.

I'm not sure if having a GH is an requirement to join an alliance as well.

Guild Hall on GuildWiki.

How hard is the Hall of Heroes? Was thinking about doing it that way since its way too expensive to buy a hall.

It would be far far easier to farm 20P to buy one.

HoH isn't PvE content, but very, very challenging PvP content, so winning that everyone can do.

As dgb mentioned, it is much easier to just farm the gold needed, than try to win at Heroes' Ascend. Of course if you are experienced with PvP and 7 as experienced friends you could try that :P

HoH is really tough, and if you're new to it, its even herder I'm not sure what the price sigels are at the moment, but I know when I bought mine, the price had dropped by 10K, i paid around 12k for mine.