Pella does'nt make a vinyl window, years ago they bought out an existing factory in Kentucky and simply put their sticker on the product.
Straight out of my reps mouth when he told me they were going to start offering vinyl replacements since they were missing a huge market without some offering.
They're not great by any means, but we sold/installed a ton of them....people bought them simply due to the sticker that said Pella, I used them as my bottom end offer/cheapest window offer and explained as to why they should really invest in the better quality units, but bottom dollar was the #1 item that based most the consumer descions around here.
We never had any call backs with them, had a few hardware issues, but that was just a simple phone call to my rep and they sent a "tech" out to take care of it...worked out great for me, big mark up and never had to look back. As with about anything, a good installer can make a POS product work whereas a hack can take the best on the market and turn it into a POS in a hurry.