Data theft isn't really a problem after rooting. It can happen regardless if its rooted or not because its normally a malware app someone installs. I recommend rooting, it helps your phone have less bloatware, opens up features, helps the phone run smoother, and you have a variety of choices of which ROM to run.
xda is the leader in development of custom ROMs and are generally trusted to put out safe stuff. They do a good job of policing themselves and you can find many options for making your phone do exactly what you want through themeing apps. Since each ROM is specific to device, xda splits them and has plenty of information on how to root and they usually have methods to unroot your phone and bring it back to stock depending on the model.
Don't be scared off of rooting, I've done it and not looked back. I know people that have the same handset as me and they ***** and moan about it sucking because they are on stock and don't know theres an option to make it run better.
edit: I haven't updated in a while and now I'm running Gingerbread, last time I tried it I was having difficulty but so far so good this ROM.
GingerSenseTazzv6 for any Eris users that care.