Yes, not having a bathtub in one bathroom of the house will most likely affect your resale value.

Yes, you need a tub for resale. Glass is a miracle worker for dividing space, especially between wet and dry areas without closing up your room and diminishing natural light. If you can combine a tub and shower area in one and divide from your toilet and vanity with glass, it will feel like an open shower with the benefit of a tub. Look closely at this photo, it is not exactly what I am saying, but I think you could see how you might make it work.
It does not matter if the tub gets wet when you shower, just as long as there is enough space for both. You basically stand under the shower head, or get a ceiling waterfall head that is straight down directionally. Could be fun and unique! For other design tips, follow my blog: Lauren's Style Library at:
http://blog.laurenjacobsendesign.com/

In general, I agree with the other comments. However, if your potential future buyers (due to location or house size) are most likely singles or couples without kids, having a nice shower instead of a tub might be an advantage.

You may have noted in the photo above that this shows a wet bath with a full room drain. With this system you can do what you want because the space where the tub has been converted to a shower can have a free standing tub brought in and set up with no plumbing connections as it can drain on the floor. You just need to have the valves on the wall to have a diverter to a ceiling drop spout over the area the tub would sit. The other advantage and the reason I use this set up is that it allows the tub not to have an overflow drain, thus you get a much deeper soaking tub than one with one. In new construction this also allows you to add the tub later when you find the right deal.

I agree with what others have said regarding a tub being good for resale. But as Eggleston pointed out, your market will have the final say. I recommend consulting with a real estate professional in your area. He/She will have a good idea of what buyers in your market want.

If I were you, I would consult with a local realtor that is very familiar with your area. They would be able to advise you accurately. I completely agree with Eggleston Farkas Architect! BUT I would allow someone familiar with your area help you make that decision. Walk in showers with double shower heads are becoming quite popular!
Cheers!
m.

Here is a thought: Since from your comments you only have one bath - I am going to ASSUME your home is small? This means NO ONE with children will want to purcahse your home - or unlikely. Correct? IF this is so, then I would get the bathroom you want - do it well and do it up right. This would more than likely be a great asset since you will more than likely end up selling to a couple or a single, unless the neighborhhood is SO appealing that someone would want to add on to it just to have the home - which would mean a second bath.

I have a friend who owns a small factory house - which has been completely redone - she recently took out the tub and installed a walk in shower - with all the bells and whistles for the bathroom - which is small - but seems MUCH larger now because of the walk in shower. Heck - I would stay there just to use the now marble bathroom! ;-)

Here is a thought: Since from your comments you only have one bath - I am going to ASSUME your home is small? This means NO ONE with children will want to purcahse your home - or unlikely. Correct? IF this is so, then I would get the bathroom you want - do it well and do it up right. This would more than likely be a great asset since you will more than likely end up selling to a couple or a single, unless the neighborhhood is SO appealing that someone would want to add on to it just to have the home - which would mean a second bath.

I have a friend who owns a small factory house - which has been completely redone - she recently took out the tub and installed a walk in shower - with all the bells and whistles for the bathroom - which is small - but seems MUCH larger now because of the walk in shower. Heck - I would stay there just to use the now marble bathroom! ;-)

Entirely depends on the style of property and potential purchasers. A generous shower is very modern and will be much more appealing to many buyers than a cramped bathroom with a small shower or a shower over the tub. Speak to an agent and look at what other properties in your area are like.