Compared to some other Middle East countries, Bahrain is not lacking in nightlife. There are pubs (in hotels) that cater for pretty much everyone with a decent variety of live music. Curently the best band are 'Native Soul' a New Zealand band who play at Rock Bottom in Juffair. Many of the other bands are Filippino.
One thing to be wary of - there are quite a few bars which are pretty sleazy and almost everywhere you'll find - mainly Thai/Fillipino girls looking for the 'rich western guy'. Of course they are not all like this but there are a lot of them. This also causes problems for other women as they don't always feel comfortable in this environment.
If you're not into pubs/clubs - there are some great restaurants and coffee shops where you can sit back and enjoy a shisha and a cappucino or whatever.