I rooted my phone about a month ago and would agree that I haven't found too many reasons to do so. My main reason was that I have the "cheapo" plan from att and I was concerned that i would accidently go over my limit of 200mb so I wanted to be able to install a firewall which required root access (using droidwall). I haven't come close to 200mb in the past month and I think that is in part to the fw, but I am pretty sure that with my usage, I wouldn't go over even without it. I also wanted to be able to install non-market apps, potentially ones that I plan to write myself (and maybe i don't need root to do that, my understanding was that I did, but I could be wrong).
There are a few other features that certain apps use root access for like Widgetsoid allows you to just click a button to reboot the device (instead of having to power off and on by holding the key). You can move ringtones /notification tones local to the phone which is nice if you use custom tones because they will always be available (they aren't available if you put them on your sd card and are accessing the card via usb).
I don't know if that is my full list, and honestly I can understand if anyone thinks that those aren't very necessary things cause my wife's phone isn't rooted and she loves the phone just as it is. Also, I am a newbie to Android, so please feel free to correct me / let me know about other non-rooted ways to do what I am doing and hopefully others can list some other reasons for rooting.
As far as there not being any custom roms out there, I just read a post on xda that some one is working on porting the droid x cyanogen rom to the bravo. I also had rooted my phone in the hopes that someone would be working on it (or even that I myself could help).
I was also intending to remove some the "bloatware" but I wasn't 100% comfortable with doing that yet. Mainly cause i wasn't sure if I really definitely didn't want everything that was there...I just use Go launcher and have a bunch of apps hidden for now since I still have plenty of space and have the apps in the auto-end list.
I love the phone btw ...but it is my first smartphone so nothing to compare it with. Hope this was helpful.