Well it's hard to say if it's the machine for you. I'm happy with mine, but everyone is different.
As far as I know, there is no way to patch the software in the E-Trac, the USB connection is just so you can save/exchange patterns and settings.
Faults, yeah, the depth reading on shallow coins outside of pinpoint mode is not very accurate, but if you switch to pinpoint it gets a lot better. This is only for relatively shallow coins, and when you go to pinpoint it is accurate. Not a deal breaker by any means but it would be great if they fixed it at some point.
It is also heavy compared to many machines. To me it's worth it, the finds I'm making make it worth that extra weight.
Oh I'm sure someday they will come out with better machines, what company doesn't? I guess your options are to either figure this is a great machine and I'm going to use it and have fun, or I will save my money forever waiting for the time they never produce anything new, so that I won't get left behind, and never go detecting. Are they coming out with anything in the near future? I don't know, check their website - I'm too busy using my E-Trac to worry about it.
Here is a suggestion - find a dealer in your area and go try one out. Have the dealer demo it and let you try it and see what you think, before you spend your money.