Is this a good airfare to Ireland?

$895 from Denver is pretty good, depending on when you are traveling (the difference between May, for example, and July - It's an ok price for May, a great price for July). Also, be sure the price you are comparing includes all taxes, fees, etc. Some sites, especially airline sites, give you a "ticket" cost, but then add the extras. Kayak.com gives total price (Orbitz does, too, but it's in the fine print). Be sure you are comparing "apples to apples". In general for summer travel these days, I figure I'm doing pretty good to get under $1000 from Denver

Thanks for the replies, I forgot to mention this is in September 2010. Is it too early to worry about airfare, will there be fall sales?

For the summer months, I think that's a good price. Depends when in September though, seems like if it was later in the month, that might be past the peak season, so you might be able to find something a little cheaper if you waited a little. What I have found in dealing with Orbitz and Priceline, is that they give you the cheapest flights Monday-Tuesdays, and Wednesday - Sundays they jack their prices back up again.
Good luck, you're going to love Ireland!