The Hi-Matic 7s is a really nice camera. I've owned two of them in the past and I really enjoyed them both (the shed picture in my gallery was taken with the 7s). I'd still have mine but it was put out of work once the Bessa arrived.
The Hi-Matic has a very sharp and fast lens, and you can operate the camera in full manual mode as long as you don't mind using a handheld meter or Sunny 16. If your meter is working you can get by with a modern 1.5 volt PX 625 battery by compensating the ISO slightly downwards. Here's a tip: if you move the ASA/ISO switch all the way to the end it will de-activate the meter.
These older Hi-Matics will often need to have the light seal material replaced, but that's an easy job that you can do yourself in about 30 minutes. Also, the shutters can sometimes be slowed or frozen by accumulated grit and grime. Again, you can probably remedy this yourself with a little effort. I'm sure other RFF members can advise you on the procedure if needed.
If you've got a clean working Hi-Matic then it should serve you well for many years. It's a dandy shooter, and often overlooked in favor of the more sought-after Canonets, Yashica Electros and Konica Auto S cameras. In my opinion, the Hi-Matic is equal to them all and is an under-rated gem.
Enjoy yours and please post some photos!