Well, I'm a Newbie and got the X-terra 30 about a month ago.
I had heard the Minelab machines were the Cadillac of detectors,
but being new, I didn't want to spring for the top of the line just yet.
I bought a used one on eBay.
My take:
1. A VERY capable and effective machine. Light weight, easy to learn.
2. Plenty of depth and sensitivity.
Depth is not a problem. I was able to find a bobby pin at 6 inches.
Most old coins are less than 6 inches in my area anyway.
I've found coins down to 10 inches.
When I first got it I made the mistake of
thinking max sensitivity was best, but way too much noise, so I scaled it back
to 7 or 8 out of 10 and it works much better.
3. Best advice is take some known targets and get to know what
signals, strength, reading, and depth you get from them, then decide what
values you want to notch out. I notched out tabs and lose some nickels, but
by doing so I eliminated a lot of trash and upped my hourly take to a much
higher level overall. By NOT digging inconsistent or "blippidy" signals
I more than doubled my take of real coins.
4. Get a decent set of headphones.
5. Minor problems: Dirt. I get dirt all over the control panel.
I've taken to placing a heavy clear-plastic bag over the panel to keep it clean.
I punch holes in it for the cable lead and the headphones, then tape it
around the handle.
(My 2-cents)
Enjoy!! - the X-30 is quite a capable machine, and I can keep up with
ANY of the more expensive models.