Migration from 1.5 to 1.6 is not trivial but this extension comes close to making it so. I had three tries at migrating my first site. Initially, I had permissions issues. Next there were problems with some section and category names which needed fixing on the 1.5 site and then finally bingo! Everything across.
My recommendation would be to get a clean, empty, 1.6 installation with sp-upgrade installed, and then zip up a copy before working as a backup because you may not get things right first time. If the migration does not work as planned, scrap everything and start again from the backup. The migration only takes a minute so starting again is a quicker option than fixing everything with edits.
Another small quirk with this version is that if the migration aborts for some reason (permissions for example) you are not given a full warning.
Anyway, sp-upgrade works well and makes a difficult task simple.
Mad4Joomla forms were good, simple and quick, but didn't have the flexibility I needed to do a complex form.
Proforms did the complex one very easily and just as quickly. A small bug which I had with the TinyMCE text editor was answered almost instantly. (use something else).
The cost is reasonable and the product excellent. Highly recommended.