I'd also love to gain some insight on this and hear what others say about form extensions. I really --HATE-- doing my own forms, but haven't been all that happy with the extensions I've tried. I've looked into Chronoforms, Mad4Joomla and BreezingForms, but it seems for all the time investment required it may just be easier to do my own.
For VERY simple needs where the form results are sent via email I used QContacts, which allows a bit customizing and has built-in capcha. It's also very easy to style.
Yeah I've been a Chronoforms user for a while, i'll give qContacts a go.
Surprised no one else has replied it seems that good forms are many times the most interaction a visitor will have to the site and they usually suck. I thought there would be some hardcore tips about this but guess not.