50mm prime or 28-75 zoom?

Can I just get your opinion on something. I've been into SLR photography for quite some months now and my only equipment has been my Nikon D80 and Nikkor 50mm f/1.8. I feel like I've sort of outgrown the lens and have been doing some research into getting a zoom that would be appropriate for the kind of photos I enjoy taking - basically portraits and event snaps. This has led me to the Tamron 28-75mm 2.8.

My question is, is it worth investing in the zoom, or can I get the same results (and become more skilled) by just sticking with the prime and 'zooming with my feet'?

Based on my experience with 35mm film, I would say it is the wrong lens. I lived with a 50mm and a 135mm and was very happy. The 50mm gave me scenics and groups - zooming with my feet as you say - while the 135, which had a pretty low f: stop - maybe 1.4 - allowed me to get in close to people's faces or catch a small group in a candid situation in normal room light where zooming with my feet would have been intrusively close or obviously disturbing. I don't think 75mm will gain you enough.

Zooming with your feet isn't always practical at an event, especially when there's a crowd to deal with. At 70mm that lens would be equal to a 105mm lens on a 35mm camera. I'd get the 28-75mm lens, personally. If you're not quite sure, you could see about renting one for a few days to see how it works for you.

Portraits, partially yes. Events, no, there's simply no room. The tamron is an interesting lens, depending on the kind of event it may not be wide enough.

If I was in the market for something like that I'd be tempted to see if I could find the old tokina 28-70 f2.6-2.8

It's really a matter of personal preference as to whether you use primes or zooms. Some of which is dictated by the type of photography you will be doing.
For portraits I'd always choose a prime over a zoom.
For events and sports I'd always choose a zoom over a prime.
In the zooms the tamron you are looking at is an excellent option. Be aware of a few things before you purchase: It is a zoom. Primes are always sharper and have better quality than any zoom. The Tamron is an outstanding zoom and far better than any of the consumer zooms on the market. It is a clean, clear, sharp lens and for it's price it is pretty amazing. It is not as clean clear and sharp as the Nikkor lens which I believe is a 24-70 f/2.8. VERY close, but the Nikkor is always your best bet. If the money isn't there for the Nikkor-the tamron is worth every penny.

As to improving your skill-it doesn't matter if you are using a zoom or a prime. Taking a photograph takes the same knowledge and skill no matter what lens you use.

As to the width of this zoom. 28mm is a huge improvement in width over the 50mm, but on a crop sensor it is still a little tight. I prefer not to drop below that tight 28mm because of natural distortion that happens. When taking photos of a building and you get the bent lines of a straight building-that distortion.
I have the tamron 17-50 f/2.8 for my crop sensor cameras and I find I get into a LOT of trouble with that wide end and I end up having to fix things in the end when I use it. You can also use that distortion to your favor if you remember to and practice it.

The 50mm is very nice for portraits but you outgrew it the moment you decided to do event photography. How are group shots working out for you? Or shots where you want to showcase the venue, either interior or exterior?

You need something wider, and for events you need the flexibility that zoom lenses offer.

The lens you're considering gets great user reviews: http://www.fredmiranda.com/reviews/showproduct.php?product=187
Nice results in a lab test, too: http://www.photozone.de/...rt--review

Personally I like to go even wider - I'd prefer the Tamron 17-50mm f/2.8