Betio is hugely overcrowded and quite intimidating at first, very third-world.  But once you get out of the car and walk around, the locals are very friendly.  Watch your step on the beach though as they still use the lagoon-side as a toilet.  Getting around Tarawa is easy - you will see lots of run-down vans pumping out loud remixes of traditional tunes.  Just flag one down and shout when you want it to stop.  You will be charged somewhere between $2-3 AU, depending on the mood of the cashier.  Make sure you are polite; most locasl speak English but if you learn some I-Kiribati, they will appreciate it.  Note: Kiribati is pronounced 'KIH-rih-bahs' (the local pronunciation of 'Gilbert' - these were once known as the Gilbert Islands).  The local food is interesting, try the various options available at the small chinese restaurants as well as Mary's in Bairiki, where we tried some interesting combinations of loca, Chinese and Japanes foods:
http://www.visit-kiribati.com/kiribati/cms/to_stay/tarawa_gilbert/marys_motel.html.  Make sure you get out and about and get used to the temperature rather than hiding in the air-conditioned rooms, as this will only make it worse when you do go out.  Other good places to stay are the Otintai and Tarawa hotels, although we stayed in a private residence so I can't review them.  Wear light clothes that cover you well, nothing that reveals your thighs.  You can get quite cheap lavalava fabric at the village shops in Bairiki, and there are various craft centres to buy souvenirs - just watch out for borer holes and make sure when they trat your souvenirs that they write what they did, as I lost one of my handcarved boats due to a borer hole and no notes on the treatment.  Customs concluded they only used flyspray and took it off me. try to get out to the other islands and see the real Kiribati, where there is no electricity but also relatively no pollution.  Don't swim in Tarawa lagoon, but there are plenty of nice spots up the Northern branch of the island, such as broken bridge (a failed Aussie Aid project)...  Don't drink too many coconuts at once and bring your Immodium :)