So, should I keep my road bike??

I have a decent road bike as well that I have set-up for Tri's (fast forward Seat post, clip-on areo bars, read hydration set-up); I plan to keep my road bike when I purchase a Tri-Bike.  For what I'd get for it on the market as a used bike, vs.  what I paid for it and add-ons it is worth more to me than I'd expect to get for it.  I am keeping mine for training and other general rides.

I was in the same situaton about a month ago. I sold my beloved Specialized Tarmac to a friend to finance a Felt B16. So I no longer have a road bike. 

Here is my justification.

I'm doing my first IM in 2012 and wanted to do so on a tri bike.

I sold the road bike for a great price and only had to invest $200 into my tri bike.  I got a great deal from a local shop who wanted to put me on a brand he sells and sponsor me for up coming races.

If I find out I really need a raod bike i will probably buy a new Felt road bike at the end of the year.

I do feel bad about selling my road bike since its still in my basement sitting beside my new tri bike. If I could have afforded both I would have kept it.  

On another note I keep seeing post about not allowing tri bike on a charity ride or century rides. That seems wierd to me, i have never encountered this.  

Thanks to all for the responses, they are very helpful!

Thankfully right now I am blessed enough to be able to afford both bikes so I may go that route.  My main thought for only one bike is just that I tend to be run-centric and thus don't get to ride as much as I'd like and so it would just seem like one of the two bikes would be sitting around not getting used much. 

Another option:

Sell the road bike, get a good tri bike but set it up like this. You get the best of both worlds and a very versatile tri bike.

Sure, a tri bike with drop bars is excellent for hills (and mountains). But if someone wants to just have one bike, it is also a good way to get great versatility out of an a aero and fast triathlon specific frame. And it makes your tri bike so much more useful (and safer) for riding in town, riding in the city, doing some errands, riding with groups. Etc. ...

If you're in the position to do it financially, keep the road bike and get a tri bike.

If, in time, one isn't getting used, sell it off. You may find you like to have the option to switch it up - or that one bike really is THE bike for you.