I found the simpler the better,I had good luck with the White's Surf 11(old model),does both water and land,but I'm just an ocassional treasure hunter.
But the only metal detector I've ever had was a Garrett. Now all the circuits on it are corroded and it's time for a new one. My choice would definitely be a White, based both on my experience with old metal dectecting buddies and on what little I've read about the newer Whites: I like the better discrimination available on them and the fact that newer models can "image" what's underground. Definitely buy the top-end White available. This will allow you to go over already searched ground and find things earlier searchers missed.
Some old links I've accumulated:
California dectecting forum (but worthwhile reading for everyone)
http://www.findmall.com/forums/
The high-end Whites' forum --- at least last time I looked the DFX was the best White
A ground-penetrating radar site
http://www.g-p-r.com/tutorial.htm
Jimmy Sierra Books and digging tools
Kellyco Metal Detecting Superstore
Noggin subsurface imaging page... Highly rated Noggin systems
The one that finds the gold.
I have always found gold metal detecting/metal detecting to be extremely exciting and and to me conveys a certain sense of searching history. I was also wondering if anyone owns an underground metal detector and would like to share their cool stories about it?
http://www.detectorall.com/categories/Walk-Through-Metal-Detectors/