Hi Inverted,
Baja is a very unique shard... for several reasons. On the list of most populous shards, Baja is in the middle... so like Oriana said, Baja isn't overcrowded but it is not empty either. You can easily find a decent house plot, but you'll have to look for it.
About the players on Baja, I find most of them less drama than other shards... they just want to play. We don't have the most active PvP, but considering our population... it is better than most. RP on Baja is minimal, but exists. Events excels on Baja, for our size... Baja is busy with events by various guilds.
Speaking of guilds, we have it all. Spawning guilds. A few mega guilds. Lots of little guilds. Handful of hardcore PvP guilds. Event guilds. PvE/PvM guilds. And some excellent legacy guilds (going back to UO's beginnings 10 years ago). Baja is a little light on pure RP guilds.
Diversity. Baja is probably the most diverse... meaning where players play from in the world. Baja of course is a US shard, so the majority of it's population is from the US. There are some players from the EU, although Baja doesn't ping so fast for EU players.
Despite the distance though, Baja pings fairly well for Asia... so Baja has a good contingent of Asian players (CH, HK, JP, KR, PH, SP, etc.) for not being an Asian shard. This makes for great place to learn different PvE/PvM/PvP techniques from one another. The talent pool of knowledgeable players on Baja is one of the best.
Hope that helps.