Favorite task chair, anyone?  

Aeron!
I'm sitting an Aeron Chair from Herman Miller, which is the most comfortable task (or office) chair ever.
I got it on eBay for under $400.00.
I also have a Mirra Chair from Herman Miller, which is fairly comfortable, but nowhere as nice as my Aeron Chair.
I think the Aeron Chair is about the most popular office chair in the US.

Aeron, eh?
I guess I was being disingenuous when I said I value comfort over looks, because I don't think the Aeron would look very good at my trim, wall-hung rosewood desk.
Frankly, I didn't even sit in one today, though I had several opportunities. I'll give one a try before making my final decision, though...

Barry is right
The Aeron is our choice for a task chair, even though we've used the aluminum group (both soft and thin pad), the Time-Life chair, the Saarinen executive chair and others. For long-term use and erganomics the Aeron is very hard to beat. It pretty much set the standard. Plus you can be thrifty and get one second hand for much less than a new one.

Yep, Barry is correct
I have an Aeron (size B), a newer Time Life chair, and an older Knoll Life? chair, and an older HM equa chair..and the comfort award easily goes to the Aeron. I never tire of sitting on it. Why can't automobiles offer the pelicle mesh as an option?

I guess I don't really LIKE the looks of task chairs, in the first place--
which is why I've been using a molded-plywood chair at my desk for years.
If I'm going to trade in looks for comfort, and pay many hundreds of dollars, I sorta want ALL the bells & whistles-- adjustable arms, back, etcetery.
The aluminum group chairs look great, but they're not adjustable or especially well-suited to long hours on the computer.
The Aeron (& Mirra, for that matter) may be comfortable, but I find the big balloon-back shapes, and meshy man-made upholstery inappropriate for my small apartment furnished with sleek wood furniture.
I want high tech performance, but low to medium-tech appearance, I guess.

WMC...many of the latest chairs are butt ugly
but the Aeron chair is 1000% beautiful, anyway you look at it. It's a truly revolutionary looking chair that's comfortablem, well made and is award winning.
I've spouted about alot of the ugly new stuff, but this chair's go what it takes.
Maybe the reason why you feel the way you do is because you're spending hours sitting on a hard plywood chair!

maarten van severen & vincent van duysen
maybe you can try these by belgian designers maarten van severen ( for Vitra )
and vincent van duysen ( for Bulo )
http://en.bulo.com/loveyouroffice/coll_seating_chair.php
http://www.vitra.com/nl-nl/home/products/.07/

Those Belgian chairs are sleek and good looking
and they don't have the athletic-shoe styling so typical of contemporary task chairs. Unfortunately, I think the chairs that resemble sneakers tend to be considerably more comfortable.

Erik...I bet
the Aeron would be much more comfortable. It's shaped to conform to the body. Your Vitra chair is so flat back and seated.

i know but
I know they look hard but they are acutally more comfortable than they look.
The Aeron looks very comfortable.
The Maarten Van Severen chair has hidden comfort as do most of his other chairs.

Form V. Function; Form wins.
I've used both the HumanScale Freedom chair and the Aeron and the Aluminum Group at work. I know i'm in the minority here, but I dont love the Aeron - in terms of comfort or looks. And yes, I adjusted it properly.
The Freedom chair was good, but I had the highback and it was just so BIG at my desk all the time. Still, prettier than the Aeron, and (to me) more comfortable.
I finally finagled an aluminum softpad from one of my coworkers. Frankly I love it, and not just because of the looks. Its comfortable, and really - all I do is sit at my computer. I dont need to adjust the arms, and I rarely need to adjust the height. I set the recline tension about halfway, and its enough that I can rock back when I need to. My only complaint is that its standard black leather - I would have preferred cherry red, or bright green or something, but maybe thats just the spring fever talking.
You might also try out the Saarinen executive seating - with the task chair base. I saw one of them at the knoll showroom in town and it looked fine and was comfy in the initial sit.

soft pad spring fever
they seem to have several colours available on vitra website
http://www.vitra.com/en-gb/office/products/soft-pad-group-ea-217-ea-219/...

Done deal
I ordered the Knoll Life, from DWR, before the Knoll sale ends (10% off plus free shipping).
After shopping the discount venues (Ebay, sit4less, AllModern.com, etc) I decided to spend a few more bucks in order to get all the particulars I want (polished aluminum frame, lumbar support).
The online "discount" chair sites are a tease-- the low prices quoted in bold apply to no-frills, armless versions. After specifying your preferences using menu tabs, the price becomes comparable to buying from Knoll or DWR. The Ebay sellers regularly use catalog photos that aren't representative of the imperfect secondhand chairs they're selling, and they're unwilling or unable to specify materials & features.
I spent a little shy of $1,000; but if I look at it on a cost-per-use basis, it's only pennies per day.

WHC....DWR's OK but
I'd suggest you buy Knoll or Herman Miller from any of the following:
http://www.hivemodern.com
http://www.retromodern.com
http://www.highbrowfurniture.com
Unlike DWR, they also don't charge tax, they honor the same Herman Miller and/or Knoll annual sales and do not charge for shipping in the U.S.
Because there's a DWR in Minnesota, if I bought from them,I'd have to pay sales tax....plus DWR doesn't carry all of the Herman Miller and/or Knoll pieces.
Of those above, Hivemodern is the most swell. I bought my 36" square Herman Miller work table from them and most of the others only show the round varieties.
http://www.hivemodern.com