Never tried iSale but I use GarageSale often and am very happy with it. Wish some of the layouts were more customizable, but its much easier to use in general than eBay's own interface and creates some really slick looking auctions. I'm not a power seller or anything, I maybe sell 10 items a year, but my non-scientific analysis seems to show that I have increased sales and final values with GarageSale over a plain looking auction and it is WAYYYY easier to post multiple similar items than on eBay's own auction builder. The full version is certainly a good value for $40 if you will be using it often. It will save you a lot of time and rake in more cash.
Edit:
As for your question if there is anything better than eBay, my simple answer is no. The main crappy thing about eBay is how much money they take from you. Usually I will list an item on eBay and Craigslist simultaneously with a slightly higher price on CL. If it sells on CL I just take it off eBay and I have myself more money and less hassle. If it doesn't sell in the 7 days on CL then I've still made most of my money on eBay. Be sure to mention you're selling locally too so your eBay customers won't be too pissed when you remove your auction.