Is it a bad idea to hike in my Saucony running shoes?

There is nothing wrong with hiking in plain old running shoes. In fact, I'm pretty sure Ray Jardine uses old Saucony's too… The reason a lot of people prefer trail runners is for the durability that trail runners have over regular "street" running shoes. Trail runners tend to have a more durable rubber, reinforcements on the outsole where a lot of abrasion comes from rocks, and wider toe boxes for more 'long distance' comfort.

However, if your running shoes fit you amazingly, then try hiking in them! You'll quickly discover how they hold up. TONS of mesh may not be a great idea in areas where you're gonna be scraping up your shoes a bunch.

I've used Sauconys. No problem.

Thanks. I will try them out on my hike this summer. I was also wondering how necessary gaiters are. Will I be miserable if I don't buy some?

Not miserable. Some areas call for gaiters more than others.

I trail run in running shoes over a hundred days a year. They work well for me in relatively non technical terrain. As the terrain gets more technical, I tend to have mild ankle rolls. For backpacking, I move to trail runners that eliminate my ankle roll. I have found trail runners very somewhat in ankle control. This is an area for you to experiment and build personal understanding. Remember that your experiment is shoe specific rather than applicable to the whole shoe category.

Gaiters, rarely use them. They introduce an element of fuss factor and I don't have issues without them. For 20+ mile days my feet need a bit more care, partially due to dust and moisture in my socks. Gaitors could help in this regard, but I wash my feet, apply powder and/or change my socks rather than wear gators.

I wear eVent gaiters in the winter to keep snow and icy water out of my goretex trail runners. In the summer I don't wear any gaiters with my mesh trail runners. Either way I'm wearing shorts.

I can see the appeal of simple packcloth gaiters in tall grass with a lot of ticks, especially if said gaiters were sprayed with permethrin. But then long pants might be better.

I hike in running shoes and find that a pair of lightweight gaiters are wonderful for avoiding the constant hassles with pebbles getting inside my shoes. I use them for trail running, too. The ones I use are from dirtygirlgaiters.com.

I don't hike in my Nikes because they put my feet so far above the earth, they tend to cause ankle roll-outs. I do hike in racing flats (Asics Piranhas) beccause they put my feet real close to the earth, but only on soft trails. On sharp, rocky trials I use Salomon Pro trail runners.

Ross, yes you can do it. But I would condition yourself first. Do some day hikes in your running shoes. You need to build up your ankle strength.
I only hike in very flexible shoes. "Barefoot" or minimalist shoes if you want to call it that. They conform to the ground you hike on and you feel everything. So, I would hardly call heavy boots a necessity.

Ken, around here in summer I wear pants AND gaiters. Pants over the gaiters. The grassy oak woodlands get infested with all kinds of nasty stickers that get in your shoes. If you wore just gaiters they would end up sliding down the top of the gaiters. If you wore just pants, they would get up and down your shoes somehow, unless you were wearing really skinny pants.