I have a limited knowledge on flashes, but enough to get by. In no means I am an expert, so heres my "weigh in".
I have the Sunpak PZ42X for Canon. I am very happy with it. The flash feels well made and sturdy on my Canon Rebel XS. I have added a battery grip which helps counter balance the weight of the flash. I have not experienced any misfires and the recycle time is very fast. I do not have any additional flashes, so can't do a full comparison.
The photo quality of the Sunpak versus the pop-up flash is astounding. The ttl does help, but I have not seen any instances where I would HAVE to have it or I am just naive to the full usage for it. If you are stuck between the PZ42X and PZ40X, I went with the PZ42X over the PZ40X because of the swivel head; whats $10 more.
Overall imo a great inexpensive flash to buy. I did a lot of research on inexpensive flashes and read a ton of reviews. The Sunpak PZ42X had a number of very good reviews on it but limited information. I would give it a "A", would have been a "A+" if there was more information on it.
I have placed a purchase on the Cactus V2s Wireless Flash Triggers to seem if they work (not too much information on the two being used together). I have received and email confirming that they should work (once again, lack of information).
Give me some time to post some pictures of the Sunpak PZ42X and the pop-up flash on the XS.