I also went there, 1973-80!
I think it's a very different beast to the one attended: for example, in my class of 30, one came from a private prep; the rest of us were from village primaries. Now I gather it's Prep Central. There's a reason why Salisbury is full of prep schools all offering 11+ preparation! And why there isn't a middle-of-the-road non religious denominational private secondary there! (So I'm excluding up-scale Godolphin and another which was the amalgamation of the girls convent, La Retraite and a boys prep called The Swan. No idea what it's called or what it's like now!).
The other issue is of course that, being a grammar area, the non-grammars are secondary moderns. I gather the girls one, St Edmunds, is good but I believe that's about it! I have no idea how strong academically your DD is but I'd say unless she's very, very clever (and obv. schooled up in NVR type tests!) she'd need to be in a private prep NOW to give her a chance of passing the 11+, for 2012 entry.
Personally, I had a good time at SWGS, though of course, being a GS, my reasonable intellect was distinctly average compared to many of the girls! The buildings were a bit grotty back then (and teh school was big- 1100 of us, loads of demountable classrooms which I believe are all gone now!). I recall Miss M the HM who was Mrs Thatcher's twin. Scary woman but I never had cause to cross her path! We had some exceptionally good teachers but of course many would've been taken to pieces in an inner city comp!