Hi Earthday
I feel somewhat qualified to comment here, given that I live and work in the Hills and have bought several units, townhouses, houses and land blocks in this area for clients and myself in the last 12 years
Baulkham Hills is a great suburb- sure there are sections you may want to stay away from due to freeway noise, poorly managed strata buildings etc but it's not different than any suburb really. Depending on your budget and your criteria you will be paying anything from mid $400K's up to mid $600K's for medium density dwellings of this nature. Units are cheaper, but investors prefer townhouses for their capacity to generally hold value better. Houses range from low $500K's through to $1m+ depending again on area, size and condition of property.
Forget counting on the rail link- it's been planned on and off since 1985 and until the first clod of earth is turned I wouldn't be relying on it as a sole incentive to invest in this area.
What this Hills suburb has going for it (as do nearby suburbs including Northmead, Winston Hills, Castle Hill, Cherrybrook etc) is price affordability, demographics mainly consisting of families, high owner-occupier population, good schools and amenities, rapid cbd bus transport (be careful when purchasing to ensure you stick to walking distance routes to major stops eg: Old Northern Rd, Castle Hill Rd) great shopping, loads of sporting grounds/parks and a generally "nice" feel.
As for others comments about suburbs without rail not appreciating as much, that's actually a myth - if you compare the average cg over the last decade in housing of a rail suburb eg: Chatswood 6.42% to Baulkham Hills 6.12% you'll see there's little difference. Sure, transport is important and I agree but it's certainly not the
only determinant of an area's capacity for potential growth. You need to also consider so many other factors.
Anyway, got to fly- just thought I'd pop in and add my 2c worth here.
Best of luck with your search.