Very Interesting discussion.
I started out using the smith for squats and bench press but then took the plunge and went to free weights. I am lucky and my gym has a squat rack although it was rarely in use for squats. The space was being used by PT's for other exercises as there is a bit of clear floor space there.
I was squatting 80Kg (3*8) in the Smith a month ago and had to drop to 60Kg with free weights in order to get the stabilisers working. I went to 80Kg but am back down to 70 at the moment due to the Achillies heal issues and a week off. Will probabily step back up to 80Kg tonight (including bar weight).
The idea of using the Smith to push past a period of no gain seems a very good one.
Some people also use the Smith for chinups.
The bench press bench I use has hooks maybe 6" above chest level which I have used a couple of times so although I exercise alone, I can still use the free weights for most things with reasonible safety.
A lot of people at my gym use the Smith. I even saw three young guys bench pressing on it with the spare two acting as extra spotters and weight changes as they rotated. They were working on average around 30Kg. Whilst being a bit of overkill in my mind it was to the saftey to weight that bothered me. I was in the squat rack next to them (which is too close to the Smith IMHO) and had to keep watching out for them moving back and forth changing weights etc when I am squatting a heavy (for me) load. If they clipped me, everything could have gone pear shaped pretty fast. I mentioned this to the gym staff and they may (possibly) move them a bit further apart.
For
G4orce, I would suggest moving from the smith and just work on the bench with free weights for the time being to build the stabilisers. Dont worry about dropping weight. I started out bench pressing a clean 20Kg bar 7 weeks ago and am now pushing 60Kg total. Sure working with the clean bar was embarassing if I let pride get to me but it soon went up. Now I am above average in the gym out of the people I have seen there. Only a few others use 20Kg discs on the bar. Ok, my point. Pushing 100Kg in the Smith probabily felt great and dropping to 40Kg feels dissapointing. I would suggest going with 40Kg on 3*8 sets until you get back up to a weight you are happier with and then reassessing what you want for the training. With good diet the 3*8 should see you getting to your Smith weights fairly quick and then you could change to 5*5 for strength or continue with the 3*8 for size. Just remember to up the weight on completion of 3*8 with good form and it will build from there. Also, remember..... the people who know their stuff know that 100Kg on a Smith does not equate to 100Kg on a free weight bench. You also know this too. Work hard and get your self up to 100Kg free weights and that will be impressive.
Just my thoughts of course

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Regards
RB