Regarding Sims, there are sims, and then there are sims.
Personally I quite easily get in an aircraft after a 15 month lay-off and fly as well as I did for the GST.
This is because I have a sim that completely as possible replicates both the aircraft I fly and also the world around me.
There are a number of 'negative' transfers that can occur. For example a long term simmer may be transfixed on the instruments during an early VFR training flight when they should be looking outside. Most of this is played up a lot though and if you are aware of it before starting in the real world it isn't much of an issue.
However, as you are starting flying training and considering a sim as an aid you can avoid most of the problems.
If you go for it buy FSX, invest in VFR photo scenery for your training area so landmarks are replicated (Horizon and Just Flight both provide VFR photo scenery, I prefer Just Flight's version). Get a decent model of the aircraft you are training in (not one provide by MS) and budget at least 2K for a decent PC to run it, rudder pedals, yoke and head tracking.
Sims at this level are very useful, be it basic co-ordination, nailing circuits or just keeping your hand in when the weather cancels 4 lessons in a row. It cannot totally replicate control inputs, but then again you can't pause or replay a real aeroplane and figure where you went wrong. The 'feel' of every real aeroplane is different in any case and I've never found it to be a problem at all that the controls are not exactly the same. Gross co-ordination is the same.
I wasn't much of a simmer when I started flying training btw, to this day I've never done a 'fantasy' flight, it's enough for me to use it to compliment real world flying. I was also advised by a guy who was evaluating FSX systems for RAF basic training - the value is there and much of what you gain from a sim is actually to do with how cleverly you choose to use it and how far you replicate the many routines that make up flying. Just being able to sit in a virtual cockpit and run through a checklist is a real bonus for example. As is making a radio call at the right time etc.
In all looking at the initial cost and what it has probably saved me during initial training and later regaining currency, I would say it was a good investment.